change channel names

[melonora]

Closes #750

This PR allows for either changing the channel_names by means of a static method on a image SpatialElement or in case of an element in the Spatialdata object a method taking as parameter the element name.

Also when channel names get written the metadata on disk is updated.

[codecov]

Codecov Report

Attention: Patch coverage is 89.33333% with 8 lines in your changes missing coverage. Please review.

Project coverage is 91.80%. Comparing base (62e4699) to head (d8cd38e).
Report is 72 commits behind head on main.

Files with missing lines	Patch %	Lines
src/spatialdata/models/_utils.py	83.33%	3 Missing ⚠️
src/spatialdata/_core/spatialdata.py	91.66%	2 Missing ⚠️
src/spatialdata/_io/_utils.py	92.30%	1 Missing ⚠️
src/spatialdata/_utils.py	88.88%	1 Missing ⚠️
src/spatialdata/transformations/operations.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #786      +/-   ##
==========================================
- Coverage   91.84%   91.80%   -0.05%     
==========================================
  Files          45       45              
  Lines        6893     6954      +61     
==========================================
+ Hits         6331     6384      +53     
- Misses        562      570       +8     

Files with missing lines	Coverage Δ
src/spatialdata/_core/operations/map.py	97.77% <100.00%> (ø)
src/spatialdata/_core/operations/transform.py	90.82% <100.00%> (ø)
src/spatialdata/_io/io_raster.py	96.06% <100.00%> (ø)
src/spatialdata/models/__init__.py	100.00% <ø> (ø)
src/spatialdata/models/models.py	87.78% <100.00%> (+0.02%)	⬆️
src/spatialdata/_io/_utils.py	87.22% <92.30%> (+0.39%)	⬆️
src/spatialdata/_utils.py	87.41% <88.88%> (+0.09%)	⬆️
src/spatialdata/transformations/operations.py	88.40% <50.00%> (-0.43%)	⬇️
src/spatialdata/_core/spatialdata.py	90.88% <91.66%> (+<0.01%)	⬆️
src/spatialdata/models/_utils.py	90.41% <83.33%> (-1.03%)	⬇️

[LucaMarconato]

Looks great! Three further minor comments:

• after renaming get_channels() to get_channel_names(), we need to:
  • update the docs
  • call automatically get_channel_names() from get_channels() and give a deprecation warning
• we need to call write_channel_names() from write_metadata()
• we need to update the test for write_metadata() to consider the channel names