GitLab Runner Drops Warning Due to Logger Initialization Order in Instance Executor

A warning meant to alert users that use_common_build_dir had no effect was never shown in CI job logs. The GitLab Runner instance executor wrote the message through an executor logger field that was not yet initialized, because it was assigned later in the Prepare method. As a result, the warning was silently discarded instead of reaching the active job trace. The fix, merged in MR !7813 for issue #40194, uses the logger already passed into the Prepare options. Table-driven tests were added to verify the warning under different VM isolation and max_use_count configurations.