[mobile] Update test model generation script to count op occurrences
This updated script will count the number of model that contains a certain op, and calculate the coverage based on that.
Example output:
Generated 693 ops
Covered 344/393 (87.53%) production ops
Covered 6053/7146 (84.7%) occurrence
pytorch ver 1.12.0.dev20220401
Also updated some test generation scripts
Pull Request resolved: https://github.com/pytorch/pytorch/pull/75155
Approved by: https://github.com/kit1980
