feat: Add generic support for Vamp and MoG prior

[canergen]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 24.73118% with 70 lines in your changes missing coverage. Please review.

Project coverage is 82.30%. Comparing base (1a026f8) to head (a8d1a30).

Files with missing lines	Patch %	Lines
src/scvi/module/base/_priors.py	23.91%	70 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3203      +/-   ##
==========================================
- Coverage   82.62%   82.30%   -0.33%     
==========================================
  Files         190      191       +1     
  Lines       16556    16649      +93     
==========================================
+ Hits        13680    13703      +23     
- Misses       2876     2946      +70     

Files with missing lines	Coverage Δ
src/scvi/module/base/__init__.py	100.00% <100.00%> (ø)
src/scvi/module/base/_priors.py	23.91% <23.91%> (ø)