SCons: Apply generated_wrapper to shader builders

[Repiteo]

Followup to #91624

Next wave of prettified/reformatted generated files is for the .glsl shaders. Kept the scope to just these, because despite having only two build scripts gles3_builders/glsl_builders, they're arguably the most complicated build scripts in the repo. They're certainly the most involved, as they utilize dedicated pytest scripts to ensure their outputs come out as expected; as such, this had to update the *_expected_full.glsl files as well. I also made sure that the pytests properly work on Windows as well (supersedes #86083 in the process).

In addition to the above, two other adjustments were made. The first and more simple of the two is adding .*_cache to .gitignore in order to broadly catch python module cache folders (removed .mypy_cache entry because that's now covered). The second was further expanding the functionality of generated_wrapper, featuring better logic for generating header guards (now its own function) & automatically formatting multiline #define to ensure their \ wrappers are right-justified (also its own function). Documentation has been added to each function as well, hopefully making their intended usage as unambiguous as possible.

[Repiteo]

Closing to be re-implemented on a wider scope in the future