refactor: Remove factory inputs

[kberat-synnada]

Description

Closes #129.

What is Changed

• Removal of factory_inputs attribute.
• Removal of factory_inputs from all Primitive and Logical models.
• Simplification on BaseModel call method.
• Corresponding tests updated.
• Minor merge bug in backend and PhysicalModel that fails main CI (unrelated to this PR) resolved.

Checklist:

• Tests that cover the code added.
• Corresponding changes documented.
• All tests passed.
• The code linted and styled (pre-commit run --all-files has passed).

[codecov]

Codecov Report

Attention: Patch coverage is 88.77551% with 11 lines in your changes missing coverage. Please review.

Project coverage is 88.64%. Comparing base (9b7b730) to head (13fa076).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
mithril/models/models.py	84.72%	11 Missing ⚠️

@@            Coverage Diff             @@
##             main     #130      +/-   ##
==========================================
- Coverage   88.75%   88.64%   -0.11%     
==========================================
  Files          61       61              
  Lines       15558    15391     -167     
==========================================
- Hits        13808    13643     -165     
+ Misses       1750     1748       -2     

Files with missing lines	Coverage Δ
...hril/backends/with_autograd/jax_backend/backend.py	82.98% <100.00%> (ø)
mithril/framework/common.py	96.68% <100.00%> (ø)
mithril/framework/logical/base.py	87.66% <ø> (-0.51%)	⬇️
mithril/framework/logical/essential_primitives.py	99.50% <100.00%> (-0.06%)	⬇️
mithril/framework/logical/model.py	97.10% <ø> (-0.39%)	⬇️
mithril/models/primitives.py	97.23% <100.00%> (-0.24%)	⬇️
mithril/models/models.py	88.68% <84.72%> (-0.02%)	⬇️