Delegate bakery implementation-specifics to bakeries

[moradology]

This PR aims to clean up Bake.py as it is central to the library's functionality. To this end, Bakery implementation specifics are handled by the bakeries themselves. There are two central components to this change:

1. Validation is delegated to implementation of bakery classes
2. bakery.bake is now used to delegate the specifics of running a pipeline to the bakeries themselves

[moradology]

Apologies for the chatter/failing CI, my pytest locally is using obviously cached files and though I've burned pyc and pycache, it persists in running old code 😭

EDIT: Just to be clear, this was hopeless stupidity on my part. Forgot the -e in pip install -e ..

[codecov]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (9667ae6) 95.53% compared to head (96d9afa) 94.80%.

Files	Patch %	Lines
pangeo_forge_runner/bakery/base.py	72.72%	3 Missing ⚠️
pangeo_forge_runner/bakery/flink.py	84.61%	2 Missing ⚠️
pangeo_forge_runner/commands/bake.py	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #175      +/-   ##
==========================================
- Coverage   95.53%   94.80%   -0.73%     
==========================================
  Files          14       15       +1     
  Lines         493      520      +27     
==========================================
+ Hits          471      493      +22     
- Misses         22       27       +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[moradology]

Traitlets is a cruel master. Where in the hell are the post_init hooks? How could they build a validation library without them!?