Propagate Hyperlight guest exit code and add e2e test

[danbugs]

Summary

• Update hyperlight-unikraft dep to pick up exit code propagation (PR Propagate guest exit codes and implement host-mediated time.sleep hyperlight-dev/hyperlight-unikraft#20) and library-level surrogates fix (PR pyhl: default surrogate process pool to 1 for library callers hyperlight-dev/hyperlight-unikraft#22)
• Use timing.exit_code from RunTiming instead of hardcoding 0 on successful runs — sys.exit(N) and unhandled exceptions now surface the correct exit code to callers
• Add hyperlight_exit_code.json test config and e2e test case validating sys.exit(42) returns 42

Microsoft Reviewers: Open in CodeFlow