Mask.regionprops property to calculate properties.

[yfukai]

I added Mask.regionprops to calculate the properties of the masked region.
Ideally we could think of

• Automatically updating the props upon mask update
• Calculating image-dependent props such as mean intensity etc

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.38%. Comparing base (5d51270) to head (4555062).
⚠️ Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #210      +/-   ##
==========================================
+ Coverage   88.22%   88.38%   +0.16%     
==========================================
  Files          51       54       +3     
  Lines        3592     3849     +257     
  Branches      617      665      +48     
==========================================
+ Hits         3169     3402     +233     
- Misses        254      267      +13     
- Partials      169      180      +11     

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[JoOkuma]

@yfukai, thanks for the PR

I left a few comments to improve the typing.

[yfukai]

I noticed that setting this as a property causes an issue with pickling, and changed this to a function.