Integration of PQuantML with hls4ml

[enlupi]

Description

This PR introduces the possibility of directly parsing PQuantML layers into hls4ml, both using the PyTorch and Keras V3 frontend. It uses HGQ2 conventions and relies on the bit_exact optimization pass to ensure correct precision is enforced and bit exactness.

Current status:

• PyTorch parsing (except hard tanh)
• Keras V3 parsing
• Testing

Type of change

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

Tests

Tests are under work.

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.