[Java]Add Support for Named Schemas in SpannerIO.Write by Enhancing Schema Retrieval

[Suvrat1629]

Please add a meaningful description for your change here

---

Modified ReadSpannerSchema to query the INFORMATION_SCHEMA.TABLES with a broader scope, including tables across all schemas by using SELECT CONCAT(TABLE_SCHEMA, '.', TABLE_NAME) AS qualified_name FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_CATALOG = ''.
Updated SpannerIO.WriteGrouped to integrate a new RewriteMutationTableNamesFn that rewrites unqualified table names to their schema-qualified equivalents based on the retrieved schema.

Closes #32907

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
• Update CHANGES.md with noteworthy changes.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

See the Contributor Guide for more tips on how to make review process smoother.

To check the build health, please visit https://github.com/apache/beam/blob/master/.test-infra/BUILD_STATUS.md

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI or the workflows README to see a list of phrases to trigger workflows.

[github-actions]

Checks are failing. Will not request review until checks are succeeding. If you'd like to override that behavior, comment assign set of reviewers

[github-actions]

Checks are failing. Will not request review until checks are succeeding. If you'd like to override that behavior, comment assign set of reviewers

[github-actions]

Checks are failing. Will not request review until checks are succeeding. If you'd like to override that behavior, comment assign set of reviewers