Remove the concurrent test prevention logic and update cleanup to use
run ID-based isolation, allowing multiple tests to run simultaneously.
Changes:
- cleanup: Add killTestContainersByRunID() to clean only containers
belonging to a specific run, add cleanupStaleTestContainers() to
remove only stopped/exited containers without affecting running tests
- docker: Remove RunningTestInfo, checkForRunningTests(), and related
error types, update cleanupAfterTest() to use run ID-based cleanup
- run: Remove Force flag and concurrent test prevention check
The test runner now:
- Allows multiple concurrent test runs on the same Docker daemon
- Cleans only stale containers before tests (not running ones)
- Cleans only containers with matching run ID after tests
- Prints run ID and monitoring info for operator visibility