Update and improve test environments

[m-albert]

The current test suite covers environments with fixed dependencies for reproducibility. However, as e.g. #429 and #427 have shown, there are problems since the testing currently

1. only covers python <=3.12
2. doesn't cover the case of python -m pip install dask-image outside of the defined test environments.

I'd suggest to

1. adapt the fixed environments more closely to the current support window https://scientific-python.org/specs/spec-0000/, e.g. testing python versions 3.10-3.14 and
2. add an environment with a current python version (e.g. 3.13) which doesn't fix the dependencies

[GenevieveBuckley]

Sounds like a good plan!