feat: DON'T review before merging previous PRs, (BitcoinRBF-Step3) zetaclient watches BTC mempool stuck txs and bump fee

[ws4charlie]

Description

This PR will replace #3306

The goals:

1. Implement BIP-125, Replace-By-Fee so that every outbound is replaceable when stuck in mempool.
2. Use the Child-Pays-for-Parent (CPFP) to bump tx fees and unblock stuck outbounds.

The fee change:

1. User still pays withdraw fee on a BTCGasPriceMultiplierFeeCharge = 2.0 multiplier.
2. TSS signers will pay lower gas fee on a BTCGasPriceMultiplierSendTx = 1.5 multiplier for quick finality.
3. The system will be able to make approximately 25% profit out of the fees paid by user, without worrying about stuck txs.

How it works:

1. Enable RBF flag in every Bitcoin outbound.
2. Spwan a new go routine WatchMempoolTxs in zetaclient to monitor pending outbound txs, so we know how long the txs have been sitting in the Bitcoin mempool.
3. If the pending period of the outbounds exceeds a pre-defined threshold (30 mins and 3 blocks), zetaclient will mark the outbound status as stuck and trigger tx replacement using RBF and CPFP.
4. After tx replacement, the outbound status will be set back to normal.
5. After tx replacement, if the outbound still doesn't move forward for another threshold period of time, RBF will triggered again with even higher fee rate until reaching a feeRateCap = 100
6. zetaclient will ALWAYS use most recent fee rate (feed by zetacore) to initiate new outbound transactions. The reason is that using an outdated GasPrice in CCTX struct is usually the root cause (not the Bitcoin network traffic) of stuck transactions, the low-fee problem needs to be solved at its root cause to reduce the chance of stuck txs. Similarly, when GasPrice in CCTX struct is higher than market, TSS signers will also use the most recent fee rate to send outbound and save gas fees.

A few concepts and parameters introduced:

1. LastPendingOutbound:
   Bitcoin outbounds are sequentially chained transactions by nonce. Given N pending txs [TX1, TX2, TX3, TX4] in the mempool, zetaclient only need to watch and bump the fee of TX4 in order to clear all of them. According to Bitcoin CPFP strategy, the chained pending txs are treated as a package by miners. Bumping TX4 will increase the average fee rate of the whole txs package and make it more attractive to miners.
2. minCPFPFeeBumpPercent:
   It is set to 20% as an exercise for the initial play. It is designed to balance effectiveness in replacing stuck tx while avoiding excessive sensitivity to fee market fluctuations. For example, given a paidRate == 10, RBF will not happen until the market rate goes up to liveRate==12.
3. feeRateCap:
   It is the maximum average fee rate for fee bumping. 100 sat/vB is a chosen heuristic based on Bitcoin mempool statistics to avoid excessive (or accidental) fees.
4. reservedRBFFees:
   It is the amount of BTC reserved in the outbound transaction for fee bumping. It is set to 0.01 BTC by default, which can bmp 10 transactions (1KB each) by 100 sat/vB. Most of the time, we have just 1 or 2 stuck transactions in the mempool and the signers will automatically stop signing new transactions by design, so the number 0.01 BTC is good enough.

Closes: #1695

• Tested CCTX in localnet
• Tested in development environment
• Go unit tests
• Go integration tests
• Tested via GitHub Actions

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[github-actions]

!!!WARNING!!!
nosec detected in the following files: zetaclient/chains/bitcoin/observer/db.go, zetaclient/chains/bitcoin/observer/gas_price.go, zetaclient/chains/bitcoin/observer/mempool.go, zetaclient/chains/bitcoin/observer/mempool_test.go, zetaclient/chains/bitcoin/signer/outbound_data.go, zetaclient/chains/bitcoin/signer/sign.go, zetaclient/chains/bitcoin/common/fee.go

Be very careful about using #nosec in code. It can be a quick way to suppress security warnings and move forward with development, it should be employed with caution. Suppressing warnings with #nosec can hide potentially serious vulnerabilities. Only use #nosec when you're absolutely certain that the security issue is either a false positive or has been mitigated in another way.

Only suppress a single rule (or a specific set of rules) within a section of code, while continuing to scan for other problems. To do this, you can list the rule(s) to be suppressed within the #nosec annotation, e.g: /* #nosec G401 */ or //#nosec G201 G202 G203
Broad #nosec annotations should be avoided, as they can hide other vulnerabilities. The CI will block you from merging this PR until you remove #nosec annotations that do not target specific rules.

Pay extra attention to the way #nosec is being used in the files listed above.

[codecov]

Codecov Report

Attention: Patch coverage is 67.17764% with 364 lines in your changes missing coverage. Please review.

Project coverage is 65.38%. Comparing base (6802bf2) to head (03d366c).
Report is 4 commits behind head on develop.

Files with missing lines	Patch %	Lines
zetaclient/chains/bitcoin/observer/outbound.go	29.62%	75 Missing and 1 partial ⚠️
zetaclient/chains/bitcoin/client/helpers.go	0.00%	60 Missing ⚠️
zetaclient/chains/bitcoin/observer/mempool.go	66.66%	44 Missing ⚠️
zetaclient/chains/bitcoin/signer/signer.go	42.25%	39 Missing and 2 partials ⚠️
zetaclient/chains/bitcoin/observer/gas_price.go	0.00%	37 Missing ⚠️
zetaclient/chains/bitcoin/client/commands.go	0.00%	26 Missing ⚠️
zetaclient/chains/bitcoin/signer/sign.go	83.64%	18 Missing and 8 partials ⚠️
zetaclient/chains/bitcoin/observer/utxos.go	84.34%	12 Missing and 6 partials ⚠️
zetaclient/chains/bitcoin/signer/outbound_data.go	90.14%	5 Missing and 2 partials ⚠️
zetaclient/chains/bitcoin/signer/sign_rbf.go	89.09%	5 Missing and 1 partial ⚠️
... and 7 more

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3396      +/-   ##
===========================================
+ Coverage    64.40%   65.38%   +0.97%     
===========================================
  Files          436      445       +9     
  Lines        30379    30879     +500     
===========================================
+ Hits         19566    20189     +623     
+ Misses        9972     9832     -140     
- Partials       841      858      +17     

Files with missing lines	Coverage Δ
pkg/math/integer.go	100.00% <100.00%> (ø)
zetaclient/chains/bitcoin/bitcoin.go	52.02% <100.00%> (+0.99%)	⬆️
zetaclient/chains/bitcoin/signer/fee_bumper.go	100.00% <100.00%> (ø)
zetaclient/chains/evm/observer/observer.go	70.28% <100.00%> (ø)
zetaclient/testutils/testdata.go	87.09% <100.00%> (+0.35%)	⬆️
zetaclient/testutils/testdata_naming.go	80.85% <100.00%> (+0.85%)	⬆️
zetaclient/zetacore/broadcast.go	59.16% <100.00%> (+0.34%)	⬆️
zetaclient/zetacore/client_vote.go	52.50% <100.00%> (ø)
zetaclient/zetacore/tx.go	83.60% <100.00%> (ø)
zetaclient/chains/evm/signer/signer.go	41.56% <0.00%> (ø)
... and 16 more