Save and load settings

[jo-mueller]

This PR adds buttons to the toolboxes which allow saving and importing parameter files.

• Tested interactively
• covered by tests
• used import/exported in example notebook.

@Schroetinger this is what we discussed earlier today :)

Also fixes #312

[codecov]

Codecov Report

Merging #314 (432b71f) into main (e0be531) will increase coverage by 0.05%.
The diff coverage is 95.18%.

@@            Coverage Diff             @@
##             main     #314      +/-   ##
==========================================
+ Coverage   82.82%   82.88%   +0.05%     
==========================================
  Files          51       53       +2     
  Lines        9266     9346      +80     
==========================================
+ Hits         7675     7746      +71     
- Misses       1591     1600       +9     

Impacted Files	Coverage Δ
src/napari_stress/_utils/import_export_settings.py	84.61% <84.61%> (ø)
src/napari_stress/__init__.py	100.00% <100.00%> (ø)
src/napari_stress/_measurements/toolbox.py	96.79% <100.00%> (+0.34%)	⬆️
src/napari_stress/_reconstruction/toolbox.py	90.06% <100.00%> (-2.00%)	⬇️
src/napari_stress/_stress/__init__.py	100.00% <100.00%> (ø)
src/napari_stress/_tests/test_measurements.py	97.63% <100.00%> (+0.04%)	⬆️
src/napari_stress/_tests/test_reconstruction.py	100.00% <100.00%> (ø)
src/napari_stress/_utils/__init__.py	100.00% <100.00%> (ø)