Add GPU arena diagnostic API
Register opted-in GPU BFC arenas and expose an experimental API to log allocator checkpoints and optionally shrink reclaimable regions.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 2c769b00-3de3-434c-9de4-6bb4c1d3760d
