Added doc strings to wandb logger

[bamblebam]

What does this PR do?

Links #9028
Adds docstrings in the wandb logger class.

Does your PR introduce any breaking changes? If yes, please list them.

None

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[bamblebam]

Does this need to be more verbose, because I think it should but I don't know how.

[codecov]

Codecov Report

Merging #9109 (ce6993a) into master (1a2468f) will decrease coverage by 4%.
The diff coverage is n/a.

❗ Current head ce6993a differs from pull request most recent head d7c8352. Consider uploading reports for the commit d7c8352 to get more accurate results

@@           Coverage Diff           @@
##           master   #9109    +/-   ##
=======================================
- Coverage      92%     88%    -4%     
=======================================
  Files         178     176     -2     
  Lines       14694   14666    -28     
=======================================
- Hits        13526   12889   -637     
- Misses       1168    1777   +609     

[tchaton]

LGTM !