ci: add ubuntu-24.04-arm runner to workflows

[vkprogrammer-001]

Changes

• Added ubuntu-24.04-arm runner to CI matrix for ARM64 architecture support
• Modified test execution to exclude electrs-dependent tests on ARM runners:
  • bdk_electrum
  • bdk_bitcoind_rpc
  • bdk_testenv
  • bdk_esplora
• Updated example builds to skip electrum-dependent examples on ARM

Rationale

This change enables CI testing on ARM64 architecture (e.g., AWS Graviton servers) while handling the architecture mismatch with the electrs binary. The electrs binary is currently only available for x86_64, causing "Exec format error (os error 8)" when attempting to run on ARM.

Future Improvements

While this solution enables CI to pass on ARM, it's a temporary workaround. Long-term improvements could include:

1. Cross-compiling electrs for ARM64
2. Refactoring tests to be architecture-aware
3. Using cargo-nextest with architecture-specific partitioning
4. Adding architecture-specific feature flags

Testing

• CI passes on both x86_64 (ubuntu-latest) and ARM64 (ubuntu-24.04-arm) runners
• Core BDK functionality is tested on both architectures
• Electrs-dependent tests are skipped only on ARM runners

Issue: bitcoindevkit/bdk_wallet#23

[vkprogrammer-001]

Hey, @notmandatory can you please review this PR? Thank you!

[YuriQueirozAndrade]

Hey @vkprogrammer-001, is this a WIP PR ? I noticed that all the commits are currently unsigned and share the same name and description. Could you please rebase and sign the commits? Also, I recommend adopting the conventional commit format for better clarity and consistency, everything I said here you can find in the contributing guide, it's worth taking a look. Other than that, everything looks good to me, cargo fmt, Clippy and all tests passed successfully. Great work!

[vkprogrammer-001]

Hi @YuriQueirozAndrade,

Thank you for catching that! I’ve addressed the issue with the unsigned commits—rebased everything and ensured the commit is now correctly signed and follows the conventional format outlined in the contributing guide.

The PR should now be all set. Appreciate the reminder about the project guidelines!

[YuriQueirozAndrade]

ACK. i run cargo clippy, fmt and test all have passed, good job!

[vkprogrammer-001]

Link to the PR in BDk wallet: bitcoindevkit/bdk_wallet#200