[bugfix] Warn if float image data being saved to non-tiff

[psobolewskiPhD]

References and relevant issues

Closes: #6670

Description

Only a subset of file types (e.g. TIFF) support float data, so if the user passes a different extension and dtype is float, then don't try saving to invalid format and instead warn the user.
Also added a test for this condition.
Also if no extension is provided and image is 3d or float, then use .tiff instead of png.

While there are skimage and imageio functions to convert arrays to int, they make assumptions, so I think this is the best way to handle this, rather than magic'ing a conversion.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.53%. Comparing base (7ebc9b4) to head (bb67146).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6884      +/-   ##
==========================================
- Coverage   92.58%   92.53%   -0.05%     
==========================================
  Files         612      612              
  Lines       55292    55315      +23     
==========================================
- Hits        51193    51187       -6     
- Misses       4099     4128      +29     

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[Czaki]

Did you validate all extensions?
Based on documentation, the .lsm should also be able to save float.