MLBEDSW-7832: test_tflite_model_semantic converting array to scalar

 - The problem is that the axis value can be either a scalar or an
array containing a single element
 - The solution is to check the length of the shape because the size
attribute returns the same value for both cases
 - This did not show up before because pytest warnings were not being
treated as errors
 - Removed pre-commit pytest option that caused tests to be searched for
from the root directory
 - Updated pyproject.toml pytest options to explicitly specify the test
directories, and to treat warnings as errors

Change-Id: I037054768e5c34f253b6062eadba1c3419ff65e4