Default to SVD for MvNormal in Latent GP conditionals

[michaelosthege]

Description

MvNormal was recently switched to default to use
cholesky decomposition which is very fragile for the higher-dimensional situations encountered in Latent GPs.

Using kwargs.setdefault() uses can still override.

Related Issue

• Closes BUG: Posterior predictive sampling of Latent GPs runs into LinAlgError at the first iteration #7754

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):

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📚 Documentation preview 📚: https://pymc--7755.org.readthedocs.build/en/7755/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.82%. Comparing base (19389fc) to head (c9a8b0b).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7755   +/-   ##
=======================================
  Coverage   92.82%   92.82%           
=======================================
  Files         107      107           
  Lines       18325    18326    +1     
=======================================
+ Hits        17010    17011    +1     
  Misses       1315     1315           

Files with missing lines	Coverage Δ
pymc/gp/gp.py	94.86% <100.00%> (+0.01%)	⬆️

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