update coverage

[reuvenperetz]

Pull Request Description:

Improve coverage:

• Raise threshold test to 97%
• Add "no cover" in cases of "internal" errors, some "repr" methods, and imports that are dependent on the framework version.
• Remove parts that are unused: identity_wrapper, _generate_images_batch
• Fix pytorch_device_config to return valid for "CPU" and add tests.
• Fix lut_fake_quant to use nbits and add tests.
• Add tests to edge matcher, logger, torch_utils, activation quantization functions, immutable class, scheduler step keras optimizer.
• Use MP for activations in tensorboard test.
• Fix name of concat threshold test to have prefix "test_".
• Add test for onnx metadata.

Checklist before requesting a review:

• I set the appropriate labels on the pull request.
• I have added/updated the release note draft (if necessary).
• I have updated the documentation to reflect my changes (if necessary).
• All function and files are well documented.
• All function and classes have type hints.
• There is a licenses in all file.
• The function and variable names are informative.
• I have checked for code duplications.
• I have added new unittest (if necessary).