Add Flatten support for NNAPI (#5545)
* Add flatten support for NNAPI, correct some typo in NNAPI code files
* Address review comments
* Update CanSkipReshape
* Add test for verify NNAPI is actually running for a supported model
* Adding test for reshape/flatten test for NNAPI
* Add one extra verbose log for skipping reshape
* Fix Android CI failure
* Correct test file name to fix Android CI failure
