Limit flask and bug fixes

[banesullivan]

Limit's flask<3 until flask_restx's python-restx/flask-restx#566 is handled.

Resolves #177

Also:

• Fixes an issue from large-image where the rasterio source is passing a CRS object to getMetdata() which isn't JSON serializable
• Drops support for extracting ROIs with the REST client as this has been broken and isn't a "rest-ful" operation.
• Drops support for histograms as it has been broken and not tested for a while

cc @dfguerrerom

[codecov-commenter]

Codecov Report

Merging #178 (1b17ede) into main (70e1a22) will increase coverage by 0.70%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             main     #178      +/-   ##
==========================================
+ Coverage   82.43%   83.14%   +0.70%     
==========================================
  Files          26       26              
  Lines        1469     1424      -45     
==========================================
- Hits         1211     1184      -27     
+ Misses        258      240      -18