VisiumHD: detect full-res image when path is relative

[quentinblampey]

There is a minor bug in the Visium HD reader. When we provide a relative path to the data, e.g. "data/Visium_HD_Mouse_Small_Intestine", then it will search for the microscopy image inside "data/Visium_HD_Mouse_Small_Intestine/data/Visium_HD_Mouse_Small_Intestine/microscope_image".

This is because it was using path / fullres_image_file instead of simply fullres_image_file.

I also did some minor updates to use pathlib everywhere instead of a combination of pathlib and os (it makes the code more readable I think).

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 45.30%. Comparing base (ed60d9f) to head (b08eb59).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/spatialdata_io/readers/visium_hd.py	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #230      +/-   ##
==========================================
- Coverage   45.31%   45.30%   -0.01%     
==========================================
  Files          22       22              
  Lines        2143     2141       -2     
==========================================
- Hits          971      970       -1     
+ Misses       1172     1171       -1     

Files with missing lines	Coverage Δ
src/spatialdata_io/readers/visium.py	19.67% <ø> (ø)
src/spatialdata_io/readers/visium_hd.py	18.29% <0.00%> (-0.39%)	⬇️

[quentinblampey]

I also set the transformation to the global coordinate system for all elements

[LucaMarconato]

Perfect, and thanks for the fix with the paths! I extended the new coordinate system mapping also to Visium data, merging now.