fix: improve error handling in global fixtures #5208

[TG199]

PR Checklist

• Addresses an existing open issue: fixes 🐛 Bug: Error in mochaGlobalTeardown is swallowed and exits with code 0 #5208
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

Description
This PR addresses an issue with the handling of errors in global teardown functions. Previously, if a global teardown function threw an error, the error was not logged clearly, and the process exit code might not reflect the failure.

Changes Made
Updated the _runGlobalFixtures method in lib/mocha.js to:
Log errors with a clear and descriptive message.
Set the process exit code to 1 when a global teardown function fails.
Improved debugging output to aid in identifying which function caused the error.
New Behavior
When a global teardown function fails:
A descriptive error message is logged.
The process exits with a non-zero code, signaling the failure.

[TG199]

All tests pass locally using npm run test-node:unit on both the main branch and my working branch. However, they fail in CI. This suggests an environment-specific issue. I'm investigating further and would appreciate any guidance on differences between the CI and local setups.