Only add total_size mapping to observed RVs

[ricardoV94]

This fixes inconsistent use of the rvs_to_total_sizes mapping. It only assigns observed_RVs to it, including the observed component of an imputed variable (even though that is not allowed at the moment).

It also raises if passed to free_RVs

Docs / Maintenance

• Cleanup total_size interface

[codecov]

Codecov Report

Merging #6331 (5468499) into main (cb37afa) will decrease coverage by 27.16%.
The diff coverage is 94.69%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #6331       +/-   ##
===========================================
- Coverage   90.39%   63.23%   -27.17%     
===========================================
  Files         111      110        -1     
  Lines       23869    23966       +97     
===========================================
- Hits        21577    15154     -6423     
- Misses       2292     8812     +6520     

Impacted Files	Coverage Δ
pymc/variational/opvi.py	75.27% <ø> (-11.81%)	⬇️
pymc/model.py	67.64% <45.45%> (-22.12%)	⬇️
pymc/distributions/continuous.py	97.84% <100.00%> (+0.33%)	⬆️
pymc/distributions/discrete.py	99.22% <100.00%> (ø)
pymc/distributions/multivariate.py	92.17% <100.00%> (-0.12%)	⬇️
pymc/tests/distributions/test_continuous.py	99.76% <100.00%> (+<0.01%)	⬆️
pymc/tests/backends/test_base.py	0.00% <0.00%> (-100.00%)	⬇️
pymc/tests/tuning/test_scaling.py	0.00% <0.00%> (-100.00%)	⬇️
pymc/tests/tuning/test_starting.py	0.00% <0.00%> (-100.00%)	⬇️
pymc/tests/backends/test_ndarray.py	0.00% <0.00%> (-100.00%)	⬇️
... and 66 more

[ricardoV94]

Superseded by #6523