impl(bigquery): wire up QueryCreationMetadata

[alvarowolfx]

Wire up generated QueryCreationMetadata and use it internally. Query::metadata() to be added in a future PR, since we are probably gonna remove query_reference.

Towards #5844

[gemini-code-assist]

Code Review

This pull request refactors the Query and CompleteQuery structures in the BigQuery crate to utilize the newly introduced QueryCreationMetadata instead of storing raw Job and QueryResponse objects. The rows field has been removed from QueryCreationMetadata (and updated in librarian.yaml), with query results now cached separately as cached_rows using a VecDeque. Additionally, helper constructors like from_job and from_query_response have been introduced, and associated tests have been updated to reflect these structural changes. There are no review comments provided, so I have no further feedback to offer.

[codecov]

Codecov Report

❌ Patch coverage is 93.84615% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.24%. Comparing base (c760f4c) to head (64298f8).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/bigquery/src/query/query_handle.rs	92.07%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6309      +/-   ##
==========================================
- Coverage   96.25%   96.24%   -0.01%     
==========================================
  Files         283      283              
  Lines       72936    72956      +20     
==========================================
+ Hits        70207    70219      +12     
- Misses       2729     2737       +8     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.