Fix redefinitions

[maresb]

Description

This is a refactor designed to make these parts of code slightly more inspectable by type checkers like mypy.

1. We use @overload to distinguish between the two distinct usages of general_toposort for which different sets of arguments are specified.
2. When a variable represents a callable, we differentiate between the variable definition and the function definition. The principle is as follows:

Worse:

if cond:
    def chosen_function()
        ...
else:
    def chosen_function()
        ...

Better:

def function_option_1():
    ...
def function_option_2():
    ...

if cond:
    chosen_function = function_option_1
else:
    chosen_function = function_option_2

The first option is worse because the definition of the underlying function changes based on the runtime logic. The second option is cleaner and more explicit because the functions are statically defined, and the choice of one or the other is made explicit.

Checklist

• Checked that the pre-commit linting/style checks pass
• Included tests that prove the fix is effective or that the new feature works
• Added necessary documentation (docstrings and/or example notebooks)
• If you are a pro: each commit corresponds to a relevant logical change

Type of change

• New feature / enhancement
• Bug fix
• Documentation
• Maintenance
• Other (please specify):

[codecov-commenter]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (ccc08ba) 80.92% compared to head (c2456c3) 80.91%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #598      +/-   ##
==========================================
- Coverage   80.92%   80.91%   -0.01%     
==========================================
  Files         162      162              
  Lines       46627    46634       +7     
  Branches    11399    11401       +2     
==========================================
+ Hits        37732    37735       +3     
- Misses       6667     6670       +3     
- Partials     2228     2229       +1     

Files	Coverage Δ
pytensor/graph/basic.py	88.76% <81.81%> (-0.33%)	⬇️
pytensor/graph/rewriting/basic.py	72.99% <33.33%> (-0.05%)	⬇️