fix(ci): test script fixes for node 22 and 26

[bshaffer]

misc test fixes needed for #9021 and #8973:

• Node 22/26 Compatibility: Scoped --no-experimental-require-module specifically to Node v22 in ci/run_conditional_tests.sh so Node v24/v26 ESM imports continue to work with c8.
• NODE_OPTIONS Preservation: Fixed ci/run_single_test.sh to append to NODE_OPTIONS rather than overwriting it, preserving parent CI environment configurations.

[gemini-code-assist]

Code Review

This pull request migrates package management and script execution from 'npm' to 'pnpm' across multiple packages, updates test coverage configurations, and enhances 'bigtable' system tests to gracefully handle 'RESOURCE_EXHAUSTED' quota errors and cleanup failures. Additionally, type casting is added to GCS headers to resolve TypeScript compilation issues. The reviewer feedback highlights several redundant nested 'try-catch' blocks in the updated test files that result in dead code, as well as a duplicated 'pnpm' installation command in a CI script.

[bshaffer]

@gemini-code-assist review please!

[gemini-code-assist]

Code Review

This pull request updates system tests to handle RESOURCE_EXHAUSTED quota errors gracefully by switching arrow functions to regular functions to support Mocha's this.skip(), adds type assertions to satisfy TypeScript compiler checks, and configures NODE_OPTIONS for Node v22. The review feedback highlights a critical issue where NODE_OPTIONS is overwritten in run_single_test.sh, discarding parent configurations, and identifies several potential resource leaks in bigtable.ts where instances or clusters are not cleaned up if tests fail before the delete calls.

[bshaffer]

@gemini-code-assist anything else?

[gemini-code-assist]

The changes in this pull request look solid and effectively address the CI stability issues, quota handling, and Node 26 compatibility. The use of try-catch blocks to handle RESOURCE_EXHAUSTED errors and gracefully skip tests is a robust approach for managing flaky CI environments.

One minor observation: your PR description mentions pinning actions/cache and actions/github-script to exact hashes for Zizmor compliance, but I don't see any changes to your GitHub Actions workflow files in the provided diffs. If those changes were intended to be part of this PR, please ensure they are included.

Otherwise, the code looks good and ready for merge.