Fix bugs in shape inference

[ricardoV94]

Description

The PyMC CI revealed two bugs in the PyTensor release:

1. A rewrite that did not handle the shape of scalars correctly introduced in the latest release in Faster infer_static_shape #521
2. A bug in the shape inference of multivariate RVs when size is not provided and the parameters batch dimensions require broadcasting. This bug was lurking for a long time now.

Related Issue

• Closes issue: #
• Related issue (not closed by this PR): #

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

Merging #546 (4dbf2e2) into main (2cef9c0) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #546   +/-   ##
=======================================
  Coverage   80.90%   80.90%           
=======================================
  Files         162      162           
  Lines       46415    46416    +1     
  Branches    11353    11354    +1     
=======================================
+ Hits        37553    37554    +1     
  Misses       6639     6639           
  Partials     2223     2223           

Files	Coverage Δ
pytensor/tensor/basic.py	88.47% <ø> (ø)
pytensor/tensor/random/op.py	96.22% <100.00%> (-0.05%)	⬇️
pytensor/tensor/rewriting/shape.py	81.53% <100.00%> (+0.10%)	⬆️