[LTC] Metrics can be reset too (#89606)
Summary:
This change allow MetricsArena to ResetMetrics too. And then rename Reset to ResetCounters given that's what it does for real.
This matches pytorch/xla#4109, and is paired with pytorch/xla#4245.
Test Plan:
CI.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89606
Approved by: https://github.com/JackCaoG
