experiment name for all views refactor

[hughes036]

Refactors to centralize experiment name and checkpoint controls on top of tabs, so that selection can apply to all views.

** Changes: **

• Pieces of state moved from TrainingModel to ExperimentModel
• ModelSelectionWidget moved to MainWidget`, Training specific controls moved back to TrainingView

** TODO: **

• More refactoring (not totally happy with ModelSelectionWidget design
• Unit testing (restore tests deleted from ModelSelectionWidget test which not belong in TrainingView test (does not exist yet))

[codecov]

Codecov Report

Merging #139 (732f14a) into main (d93e518) will decrease coverage by 0.56%.
The diff coverage is 88.60%.

❗ Current head 732f14a differs from pull request most recent head d28141a. Consider uploading reports for the commit d28141a to get more accurate results

@@            Coverage Diff             @@
##             main     #139      +/-   ##
==========================================
- Coverage   86.31%   85.76%   -0.56%     
==========================================
  Files          66       66              
  Lines        2419     2423       +4     
==========================================
- Hits         2088     2078      -10     
- Misses        331      345      +14     

Files	Coverage Δ
...l_segmenter/_tests/fakes/fake_experiments_model.py	92.85% <100.00%> (+8.24%)	⬆️
...segmenter/_tests/services/test_training_service.py	100.00% <100.00%> (ø)
...ter/_tests/training/test_image_selection_widget.py	100.00% <100.00%> (ø)
...lencell_ml_segmenter/_tests/training/test_model.py	100.00% <100.00%> (ø)
...ter/_tests/training/test_model_selection_widget.py	97.56% <100.00%> (-2.44%)	⬇️
src/allencell_ml_segmenter/constants.py	100.00% <100.00%> (ø)
src/allencell_ml_segmenter/core/event.py	100.00% <100.00%> (ø)
.../allencell_ml_segmenter/curation/curation_model.py	57.37% <ø> (-0.69%)	⬇️
src/allencell_ml_segmenter/curation/input_view.py	84.81% <ø> (-0.19%)	⬇️
src/allencell_ml_segmenter/curation/main_view.py	96.62% <100.00%> (-0.04%)	⬇️
... and 9 more