feat: do not elevate valued scalar inputs to upper level models

[norhan-synnada]

Description

Closes #37.

What is Changed

• Valued Scalar input connections are no longer lifted as inputs of the upper level wrapper models.
• Dict conversion functions updated, minor bugs fixed.
• Empty model check is converted from controlling input keys to controlling output keys.
• Multi-write check strategy updated. Input keys can be set by other valued scalar connections from now on (this was not the case!). But 2 new conditions added in order to reflect multi-write conditions more clearly.

Checklist:

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

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 98.14815% with 1 line in your changes missing coverage. Please review.

Project coverage is 86.42%. Comparing base (a497c8c) to head (99b226a). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
mithril/framework/common.py	90.00%	1 Missing :warning:

@@            Coverage Diff             @@
##             main      #49      +/-   ##
==========================================
- Coverage   86.46%   86.42%   -0.04%     
==========================================
  Files          61       61              
  Lines       15378    15368      -10     
==========================================
- Hits        13296    13282      -14     
- Misses       2082     2086       +4     

Files with missing lines	Coverage Δ
mithril/framework/codegen/numpy_gen.py	95.72% <100.00%> (-0.46%)	:arrow_down:
mithril/framework/logical/base.py	88.38% <100.00%> (ø)
mithril/framework/logical/model.py	96.66% <100.00%> (+0.11%)	:arrow_up:
mithril/framework/physical/model.py	90.63% <100.00%> (-0.97%)	:arrow_down:
mithril/models/primitives.py	97.17% <ø> (ø)
mithril/utils/dict_conversions.py	88.74% <100.00%> (-0.05%)	:arrow_down:
mithril/framework/common.py	95.96% <90.00%> (-0.04%)	:arrow_down: