Move test_mast_compat.py to tests/fb/ for internal-only tests (#358)

Summary:
Pull Request resolved: #358

Move test_mast_compat.py from tests/cpu/ to tests/fb/ because it imports
from tritonparse.fb.utils which is an internal-only module not available
in OSS. This fixes the ModuleNotFoundError in OSS CI:
  ModuleNotFoundError: No module named 'tritonparse.fb'

Reviewed By: peiying779

Differential Revision: D96222276

fbshipit-source-id: dd42e8bdb0918838a84e78bc86f82c73060b2c8f

Author: FindHao