Add support for Florence-2 training (#40914)
* Support training florence2
* update doc and testing model to florence-community
* fix florence-2 test, use head dim 16 instead of 8 for fa2
* skip test_sdpa_can_dispatch_on_flash
* Apply style fixes
---------
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
