Use ComplexityMeasures 3.8

Fixes #394, and closes #393. ## What does this PR do? Many files have changed, but mostly due to syntax changes for Documenter.jl (see comment below). The rest of the changes are: - [x] Upgrade dependency version requirement from ComplexityMeasures which was hardcoded at 3.7 up to 3.8. - [x] Quick fix: Moved GroupSlices code into a utils file in Associations.jl, since it no longer exists in ComplexityMeasures v3.8. - [x] Use StableRNG for some tests, which were occasionally failing due to random data generation. - [x] Use checkout action v5. - [x] Set minimum julia version to long term stable release (1.10.10). - [x] The necessary changes add up to quite a bit more than a simple bug fix, so I upped the minor version. ## Status - [x] Test pass - [x] Documentation build is successful. I still need to fix this. Work underway.