docs: cleanup documentation

[agoose77]

This PR

• cleans up docstrings that were wonky, or missing fields. I didn't check them hugely for meaning; this was just a quick pass over the arguments lists.
• addresses quirks in user-guide

I need to ping Martin to check some of the parquet/arrow parts.

Partially addresses #1916
Fixes #1893

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📚 The documentation for this PR will be available at https://awkward-array.readthedocs.io/en/agoose77-docs-touch-ups/ once Read the Docs has finished building 🔨

[agoose77]

This only touches docs, so it doesn't run any of the build tests. There doesn't seem to be a sane way to specify conditional required tests. We could make all workflows run for every PR, and skip every step if the job is not required, but that will bloat all of our workflows

[codecov]

Codecov Report

Merging #1946 (dc0f91e) into main (65ffb92) will increase coverage by 0.01%.
The diff coverage is 72.72%.

Additional details and impacted files

Impacted Files	Coverage Δ
src/awkward/highlevel.py	72.78% <ø> (ø)
src/awkward/operations/ak_argcartesian.py	78.94% <ø> (ø)
src/awkward/operations/ak_argcombinations.py	81.25% <ø> (ø)
src/awkward/operations/ak_argsort.py	100.00% <ø> (ø)
src/awkward/operations/ak_backend.py	100.00% <ø> (ø)
src/awkward/operations/ak_broadcast_arrays.py	100.00% <ø> (ø)
src/awkward/operations/ak_cartesian.py	89.76% <ø> (ø)
src/awkward/operations/ak_categories.py	100.00% <ø> (ø)
src/awkward/operations/ak_combinations.py	92.85% <ø> (ø)
src/awkward/operations/ak_concatenate.py	96.03% <ø> (ø)
... and 60 more

[jpivarski]

These are all improvements, with one exception, noted below. If it's hard to specify an exception to the auto-formatting (black?), it can stay.