Migrate PartitionMetadataProvider code generation from endpoints.json to partitions.json.

Motivation and Context

Currently, the GeneratedPartitionMetadataProvider is being generated from endpoints.json. Endpoints.json is legacy and adds latency during client initialization, this PR migrates PartitionMetadataProviderGenerator to use partitions.json as the data source instead.

Modifications

• Updated RegionGenerationMojo to pass partitions.json data to the PartitionMetadataProviderGenerator
• Updated PartitionMetadataProviderGenerator to read partition data from partitions.json instead of endpoints.json to generate 'GeneratedPartitionMetadataProvider' class

Testing

• Verified generated GeneratedPartitionMetadataProvider includes all 8 partitions and compiles successfully
• All current region-testing tests passed with new partition metadata provider generation.

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed
• I have added a changelog entry. Adding a new entry must be accomplished by running the scripts/new-change script and following the instructions. Commit the new file created by the script in .changes/next-release with your changes.
• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license