Make auto default precision for pytorch parser

[JanFSchulte]

Continuation of Jovan's PR #1016 that made auto the default precision in the keras parser in name mode. This PR makes the same changes for the pytorch parser.

Type of change

• New feature (non-breaking change which adds functionality)

Tests

Verified that precision is set to auto when parsing a model in name mode with the config_from_pytorch_model function.

Checklist

• I have read the guidelines for contributing.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have installed and run pre-commit on the files I edited or added.
• I have added tests that prove my fix is effective or that my feature works.