Increase gateway identifiers limit

[adriansmares]

Summary

References https://github.com/TheThingsIndustries/lorawan-stack-support/issues/1003

Changes

• Increase the limit of gateway identifiers in the assert rights call to 100 entities, as batch gateway stats RPC allows up to 100 entities.
  • The limit for the batch deletion can stay at 20, and in line with the batch device end deletion limits.

Testing

N/A. This is just an API definition change - take a look at the generated code for review purposes.

No explicit testing is required.

Regressions

This handles a regression in itself. I would say that allowing 100 entities in an RPC which is guaranteed to be served by the read replica is acceptable and fine.

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.
• The steps/process to test this feature are clearly explained including testing for regressions.
• 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.

[KrishnaIyer]

Sounds good to me.