fix(benchmarks): ensure manager.stop() is called on success path
The previous commit incorrectly changed from `finally:` to `except:`, which meant
manager.stop() was only called when there was an exception. This caused benchmarks
to appear complete but never properly finish when they succeeded. Using try-except-finally
ensures both proper exception propagation and cleanup in all cases.
Co-authored-by: McPatate <9112841+McPatate@users.noreply.github.com>