test(bigtable): adopt run-test runner for bigtable

[danieljbruce]

Description

• Updated test, system-test, and snippet-test scripts in handwritten/bigtable/package.json to invoke bin/run-test.cjs instead of calling mocha / c8 mocha directly.

No additional library or test changes were necessary because the proxyquire require shim (bin/proxyquire-bun-shim.cjs) already handles module stubbing and cache isolation across Bigtable's unit test suite under Bun. Additionally, the introduction of the --exit flag in bin/run-test.cjs ensures the test runner terminates cleanly after tests complete despite background OpenTelemetry metric timers and gRPC mock server handles.

Impact

This change enables the @google-cloud/bigtable test suites to run seamlessly under both the Node.js and Bun runtimes via the centralized bin/run-test.cjs test runner.

Testing

• Ran bun --bun run test in handwritten/bigtable and verified that all unit tests pass under the Bun runtime.
• Verified that unit tests continue passing under the Node.js runtime via node ../../bin/run-test.cjs.

[danieljbruce]

/gemini review

[gemini-code-assist]

Code Review

This pull request updates the test scripts in handwritten/bigtable/package.json (snippet-test, system-test, and test) to execute using a custom test runner script node ../../bin/run-test.cjs instead of calling mocha or c8 mocha directly. There are no review comments, and I have no feedback to provide.

[gemini-code-assist]

Code Review

This pull request updates the test scripts in handwritten/bigtable/package.json to run via a centralized test runner script (node ../../bin/run-test.cjs). Feedback on these changes points out that replacing c8 mocha with the new runner in the test script removes code coverage reporting, and suggests wrapping the new command with c8 to restore it.