Fix measure performance frequency + Add loss log

[EmanueleGhelfi]

Description

Fixes #58 Fixes #57 Fixes #53 Fixes #60

Fixes examples (they were broken)

Type of change

Please delete options that are not relevant.

• [x] Bugfix (i.e., a non-breaking change which fixes an issue)
• [x] New feature (i.e., a non-breaking change which adds functionality)
• [ ] Breaking change (i.e., a fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented on my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules

[EmanueleGhelfi]

Work in Progress

[codecov[bot]]

Codecov Report

Merging #56 into master will increase coverage by 0.49%. The diff coverage is 74.74%.

@@            Coverage Diff             @@
##           master      #56      +/-   ##
==========================================
+ Coverage   86.67%   87.17%   +0.49%     
==========================================
  Files          56       56              
  Lines        2162     2206      +44     
==========================================
+ Hits         1874     1923      +49     
+ Misses        288      283       -5     

Impacted Files	Coverage Δ
src/ashpy/layers/attention.py	100.00% <ø> (ø)
src/ashpy/layers/instance_normalization.py	100.00% <ø> (ø)
src/ashpy/callbacks/classifier.py	50.00% <33.33%> (-14.29%)	:arrow_down:
src/ashpy/trainers/gan.py	67.97% <55.00%> (-1.72%)	:arrow_down:
src/ashpy/trainers/classifier.py	87.50% <66.66%> (-0.66%)	:arrow_down:
src/ashpy/losses/executor.py	71.60% <72.72%> (+18.66%)	:arrow_up:
src/ashpy/losses/gan.py	77.69% <88.00%> (+2.69%)	:arrow_up:
src/ashpy/trainers/trainer.py	92.99% <92.30%> (+0.45%)	:arrow_up:
src/ashpy/losses/classifier.py	100.00% <100.00%> (ø)
src/ashpy/metrics/classifier.py	100.00% <100.00%> (ø)
... and 4 more

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