DOCS-2488: Add param, return override support

[andf-viam]

Add ability to override parameter descriptions and/or return descriptions, using (param|return) override files.

• Each SDK requires slightly-different override logic, see script comments.
• Also cleans up override file detection logic for before and after overrides: simpler, shorter, less filesystem traversal.
  • Important: no longer supporting omitting literal string before for before-type overrides, we need this explicitness to support new param|return override filepath detection.

Note:

• If you are seeking to populate a bunch of param|return override files, see the notes in the script: you can uncomment print statements to get the full expected override path for each param|return to make populating these much easier.
  • Even better, you can now use something like the following to create all necessary param | return override files for you:

     ## Uncomment relevant print(param|return_desc_override_file) line for the SDK you want. Then run:
     for filename in `python3 .github/workflows/update_sdk_methods.py -o go motion`; do touch $filename; done
     ## All Go > Motion override files will be created for you. Copy and paste your content into them.
    

• Not 100% sure we're matching all possible Go return data types. Will fix during arm, robot, and app re-generation shortly if so.

[viambot]

You can view a rendered version of the docs from this PR at https://docs-test.viam.dev/3019