Add support for co-adding with squared weights

[mcara]

This PR adds support for resampling and adding resampled (error, variance) images with squared weights. This is to facilitate standard error propagation.

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 99.68%. Comparing base (d6fc5bd) to head (7574641). :warning: Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #163      +/-   ##
==========================================
+ Coverage   97.51%   99.68%   +2.17%     
==========================================
  Files           3        2       -1     
  Lines         241      321      +80     
==========================================
+ Hits          235      320      +85     
+ Misses          6        1       -5     

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[mcara]

Regression tests:

JWST: https://github.com/spacetelescope/RegressionTests/actions/runs/17073575486 Roman: https://github.com/spacetelescope/RegressionTests/actions/runs/17073538185