Adding moments for AsymmetricLaplace and SkewNormal

[jlopezarriaza]

Adding the moments for the AsymmetricLaplace and SkewNormal distributions along with corresponding tests.

[codecov]

Codecov Report

Merging #5188 (6079ffe) into main (275c145) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #5188      +/-   ##
==========================================
+ Coverage   78.09%   78.11%   +0.01%     
==========================================
  Files          88       88              
  Lines       14149    14186      +37     
==========================================
+ Hits        11050    11081      +31     
- Misses       3099     3105       +6     

Impacted Files	Coverage Δ
pymc/distributions/continuous.py	96.50% <100.00%> (+0.11%)	⬆️
pymc/distributions/discrete.py	98.33% <0.00%> (-1.10%)	⬇️
pymc/bart/pgbart.py	96.24% <0.00%> (-0.38%)	⬇️
pymc/smc/smc.py	98.30% <0.00%> (-0.05%)	⬇️
pymc/initial_point.py	100.00% <0.00%> (ø)
pymc/distributions/multivariate.py	71.47% <0.00%> (+0.19%)	⬆️

[ricardoV94]

Looks great 👍