Fix dataloader table names

[LLehner]

The ImageTilesDataset class cannot be used if the table you want to work with is not called "table", since there are lines where this name is hard-coded, even though the class allows for a table_name to be specified.

An example where this fails is if you follow this tutorial but specify a different table name when creating the dataset.

This PR replaces instances of "table" with table_name.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 91.83%. Comparing base (f9fd885) to head (69c9f34).

Files	Patch %	Lines
src/spatialdata/dataloader/datasets.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #654      +/-   ##
==========================================
+ Coverage   89.95%   91.83%   +1.87%     
==========================================
  Files          44       44              
  Lines        6769     6770       +1     
==========================================
+ Hits         6089     6217     +128     
+ Misses        680      553     -127     

Files	Coverage Δ
src/spatialdata/dataloader/datasets.py	90.29% <80.00%> (+56.63%)	⬆️

... and 1 file with indirect coverage changes

[LucaMarconato]

Thanks @LLehner for the contribution. Only minor adjustments were neeed. Merging now and fixing the docs before release.