Expose band definitions via api

[ysmilda]

Summary

Closes #5403

Changes

• Add rpc to list all bands
• TBD

Testing

TBD

Regressions

n/a

Notes for Reviewers

...

Checklist

• [ ] Scope: The referenced issue is addressed, there are no unrelated changes.
• [ ] Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• [ ] Documentation: Relevant documentation is added or updated.
• [ ] Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• [ ] Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.