[test only] chore: onboard a new library

[zhumin8]

Add numberregistry library.
This is a test PR, not meant to be merged in.

Steps taken:
librarian update sources.googleapis
librarian add google/cloud/numberregistry/v1alpha
librarian install
librarian generate numberregistry

[gemini-code-assist]

Code Review

This pull request introduces the Google Cloud Number Registry Client for Java, adding the new java-numberregistry library along with its BOM, parent POM, GRPC, and Proto modules. It also registers the new library in the main GAPIC libraries BOM. The feedback highlights an incomplete description of the service in the README.md file and a typo in a Javadoc code snippet within CloudNumberRegistrySettings.java where OperationalTimedPollAlgorithm should be corrected to OperationTimedPollAlgorithm.