Switch from ZIP 32 account indices to UUID account identifiers

[str4d]

This PR is opened against main as a draft solely so it can be pre-reviewed. Once #1632 is complete and merged, I'll rebase this branch and then retarget it against a feature branch (so we can review and merge it before the backing Rust changes are released).

Closes #1633.

Author

• Self-review your own code in GitHub's web interface¹
• Add automated tests as appropriate
• Update the manual tests² as appropriate
• Check the code coverage³ report for the automated tests
• Update documentation as appropriate (e.g README.md, Architecture.md, etc.)
• Run the demo app and try the changes
• Pull in the latest changes from the main branch and squash your commits before assigning a reviewer⁴

Reviewer

• Check the code with the Code Review Guidelines checklist
• Perform an ad hoc review⁵
• Review the automated tests
• Review the manual tests
• Review the documentation, README.md, Architecture.md, etc. as appropriate
• Run the demo app and try the changes⁶

Footnotes

1. Code often looks different when reviewing the diff in a browser, making it easier to spot potential bugs. ↩

2. While we aim for automated testing of the SDK, some aspects require manual testing. If you had to manually test
   something during development of this pull request, write those steps down. ↩

3. While we are not looking for perfect coverage, the tool can point out potential cases that have been missed. Code coverage can be generated with: ./gradlew check for Kotlin modules and ./gradlew connectedCheck -PIS_ANDROID_INSTRUMENTATION_TEST_COVERAGE_ENABLED=true for Android modules. ↩

4. Having your code up to date and squashed will make it easier for others to review. Use best judgement when squashing commits, as some changes (such as refactoring) might be easier to review as a separate commit. ↩

5. In addition to a first pass using the code review guidelines, do a second pass using your best judgement and experience which may identify additional questions or comments. Research shows that code review is most effective when done in multiple passes, where reviewers look for different things through each pass. ↩

6. While the CI server runs the demo app to look for build failures or crashes, humans running the demo app are
   more likely to notice unexpected log messages, UI inconsistencies, or bad output data. Perform this step last, after verifying the code changes are safe to run locally. ↩

[str4d]

Force-pushed to rebase on main afer #1641 was merged.

[HonzaR]

The encode_usk function in lib.rs still works upon ZIP32 account index, while it needs to switch to the new account_uuid logic to align with the updated JniUnifiedSpendingKey class on the Kotlin side. @str4d can you please make this change as part of this PR? My current branch 1632-remove-default-account is built on these changes.

[HonzaR]

We need to ensure that this is fulfilled as part of this PR.

[nuttycom]

Nit: the hd_account_index and seed fingerprint go together, as they're the two necessary bits of HD derivation information.

[daira]

Unfinished but looks good so far. Please add a Zip32AccountIndex class to replace Int for ZIP 32 account indices.

[str4d]

utACK 7a064ec. Any further changes can be made in subsequent PRs to the feature branch.

[nuttycom]

post-hoc ACK, but before release we should remove the Account parameter from createSpend etc. and look those up based on the USK.

[daira]

Post-hoc ACK with comments. Follow-up tickets: #1651, #1652, #1654, #1655.