segmentation output folder should be automatically suggested/created

[Abe404]

My personal suggestion is to create a “results” folder within each project folder that contains a segmentation folder within it that perhaps also includes the model number in the folder name. For example projects/project_name/results/seg_model_10

It's not clear for users that this is a sensible action. The results and segmentation output folders should be automatically populated in the segment folder fields (when the widget is opened) and then the folder should be created if it does not already exist.

See related discussion here: #114

[Abe404]

Requirements:

• The segment folder widget model selection button should appear above the output folder selection button.
• The segment folder widget output folder button should be disabled until a model is selected.
• The segment folder output folder should be given a default (automatically populated) value once a model is selected.
  • For a model /rp_sync/projects/project_a/models/000004_1685012907.pkl the output folder would be /rp_sync/projects/project_a/results/segmentations_model_4
  • If multiple models are selected, the output folder would be /rp_sync/projects/project_a/results/segmentations_model_4_5_6_7_8
  • If the model has been renamed by the user i.e it is not 000004_1685012907.pkl but user_model_name.pkl then we include the user-specified name(s) verbatim.
• The suggested output folder can be modified by the users, i.e this is just the initially suggested output folder. The user can still click 'select output folder' and specify another folder if they wish.
• The folder (and required parent folders) of the suggested output folder will be automatically created (if they dont exist when the user clicks segment).

[Abe404]

Doing this work in a new branch https://github.com/Abe404/root_painter/compare/auto_suggest_output

Select model now appears above specify output folder: 9f983f5