[Feature]: Expose ConvertSubnetToL1 cmd

[owenwahlgren]

Issue Description

Existing Subnets need an upgrade path to L1. The ConvertSubnetToL1 functionality exists when creating a new chain, but is not exposed independently.

Solution

Expose ConvertSubnetToL1 under blockchain cmd.

avalanche blockchain convertSubnetToL1

1. Ensure ValidatorManager is properly deployed
2. Select subnet's control keys (Ledger signing needed for mainnet)
3. Submit P-Chain ConvertSubnetToL1 txn with current validator set as bootstrap
4. Ensure P-Chain PAYG balance for validators

[meaghanfitzgerald]

Current validator set cannot be submitted as bootstrap, since their NodeID is already actively associated with that SubnetID. In order for an existing Subnet to be converted to an L1, they need to bootstrap new node infrastructure, include these new nodes as part of the L1Validator[] struct in ConvertSubnetToL1Tx, and after successful conversion, let existing Subnet nodes expire, or remove with Owner Key using RemoveSubnetValidatorTx.

[meaghanfitzgerald]

Conversion from Subnet to L1 could be accomplished utilizing a similar ingestion of Subnet information to that proposed in #2378. Once the CLI has the Subnet's necessary configurations, it could spin up however many bootstrap nodes the Owner wants, and once they are bootstrapped, the user would only need to broadcast the ConvertSubnetToL1Tx, restart their L1 validator nodes, and remove their Subnet validator nodes.

This could potentially be a CLI command, but ConvertSubnetToL1Tx could also be broadcast using a script written with the sdk. Additionally, very few users will rely on the CLI for an end-to-end existing Subnet to L1 conversion, given that (once importing subnet configs is supported) all other steps will be executable with the CLI.

[meaghanfitzgerald]

Alternatively, we could have a command like your original suggestion:

avalanche blockchain convert

that builds and signs the transaction given the user provides valid:

1. Subnet Configuration with working RPC
2. Owner Key with P-Chain Avax
3. Node Credentials for L1Validators[]
4. Staking token if converting to PoS
5. Address of VMC on Subnet Chain (unless ACP 99 has been activated)

This command cannot be added until #2378 is completed.