[Unified Compiler] Renaming `python_compiler` into `unified_compiler`

[PietropaoloFrisoni]

This PR should be merged along with this PR in PennyLane

Context: This PR updates Catalyst since the python.compiler module in PennyLane has been renamed unified.compiler

Description of the Change: As above.

Benefits: Better name.

Possible Drawbacks: None that I can think of.

Related GitHub Issues: None.

[sc-98172]

[codecov[bot]]

Codecov Report

:x: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 97.35%. Comparing base (d89dfca) to head (c222d22). :warning: Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
frontend/catalyst/compiler.py	50.00%	1 Missing and 1 partial :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1997   +/-   ##
=======================================
  Coverage   97.35%   97.35%           
=======================================
  Files          88       88           
  Lines        9919     9919           
  Branches      945      945           
=======================================
  Hits         9657     9657           
  Misses        207      207           
  Partials       55       55           

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[paul0403]

@isaacdevlugt any more work needed on this one?