tests: add slow test detection and warnings to TAP output

tests: add slow test detection and warnings to TAP output

Add timing thresholds to detect slow-running tests:
- Warn for tests taking >30 seconds (slow threshold)
- Warn for tests taking >60 seconds (very slow threshold)

This helps identify performance regressions and tests that may
need optimization or may be hanging.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>