fix(ci): add matrix sharding to import profiler workflow

[hebaalazzeh]

Overview

This PR implements static matrix sharding for the import-profiler workflow to run modified packages in parallel across 8 shards, speeding up CI execution time on multi-package PRs.

Key Changes

• Parallel Sharding: Updated .github/workflows/import-profiler.yml to split modified packages under packages/ across 8 GitHub Actions runner matrix shards using modulo logic (idx % TOTAL_SHARDS).
• Unified Status Check: Added an all-import-profiles aggregation job that depends on the matrix run (needs: import-profile) to serve as the single required GitHub status check for branch protection and merge queue rules.

[gemini-code-assist]

Code Review

This pull request increases the --fail-threshold value from 5000 to 120000 in ci/run_single_test.sh when executing the profiler script. The feedback suggests double-quoting the ${PROFILER_SCRIPT} and ${PACKAGE_NAME} variables to prevent potential word splitting and globbing issues.

[parthea]

Can you create an example PR which includes changes to packages so we can see the results? Right now we only see No packages assigned to Shard 0. which is expected, but it would be great to see an example

[hebaalazzeh]

Can you create an example PR which includes changes to packages so we can see the results? Right now we only see No packages assigned to Shard 0. which is expected, but it would be great to see an example

see: #17936

[parthea]

In the demo PR, I see these errors. If that's expected, can we make the error more user friendly?

https://github.com/googleapis/google-cloud-python/actions/runs/30484508360/job/90686692668?pr=17936

/home/runner/work/_temp/1fd2f340-51ce-4adb-b3d4-044836d51fd7.sh: line 12: [: SHARD_INDEX: integer expression expected
/home/runner/work/_temp/1fd2f340-51ce-4adb-b3d4-044836d51fd7.sh: line 12: [: SHARD_INDEX: integer expression expected
/home/runner/work/_temp/1fd2f340-51ce-4adb-b3d4-044836d51fd7.sh: line 12: [: SHARD_INDEX: integer expression expected
/home/runner/work/_temp/1fd2f340-51ce-4adb-b3d4-044836d51fd7.sh: line 12: [: SHARD_INDEX: integer expression expected
/home/runner/work/_temp/1fd2f340-51ce-4adb-b3d4-044836d51fd7.sh: line 12: [: SHARD_INDEX: integer expression expected
/home/runner/work/_temp/1fd2f340-51ce-4adb-b3d4-044836d51fd7.sh: line 12: [: SHARD_INDEX: integer expression expected
/home/runner/work/_temp/1fd2f340-51ce-4adb-b3d4-044836d51fd7.sh: line 12: [: SHARD_INDEX: integer expression expected
/home/runner/work/_temp/1fd2f340-51ce-4adb-b3d4-044836d51fd7.sh: line 12: [: SHARD_INDEX: integer expression expected
No packages assigned to Shard 4.