Refactor dataset configuration code as constructors

[h-mayorquin]

As discussed in #569

#569 (comment)

This should keep code that is related together and simplify code navigation.

[CodyCBakerPhD]

I think this pattern does indeed look much better, and is more standard/consistent with other class constructors in our ecosystem too

One small comment about the annotation typing for the return

[codecov]

Codecov Report

Merging #659 (a8ea15f) into main (badf452) will increase coverage by 0.00%.
Report is 2 commits behind head on main.
The diff coverage is 88.23%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #659   +/-   ##
=======================================
  Coverage   91.61%   91.62%           
=======================================
  Files         107      107           
  Lines        5630     5646   +16     
=======================================
+ Hits         5158     5173   +15     
- Misses        472      473    +1     

Flag	Coverage Δ
unittests	91.62% <88.23%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...roconv/tools/nwb_helpers/_dataset_configuration.py	90.62% <77.77%> (+0.62%)	⬆️
...euroconv/tools/nwb_helpers/_models/_base_models.py	96.74% <90.47%> (-3.26%)	⬇️

[CodyCBakerPhD]

Interesting - automerge did not trigger when a job was manually cancelled (having some kind of intermittent stall problem with mac runners...) even after all conditions passed