GH-48095: [Python][Docs] Add missing {pyarrow,compute} functions to API docs (#48117)

Issue #48095 and #45322
 
### Rationale for this change
Missing API doc entries. 

### What changes are included in this PR?
I've added strings for functions and options to the API doc page.

### Are these changes tested?
I've built docs locally.

### Are there any user-facing changes?
Docs only.
* GitHub Issue: #48095
* Also covers: #45322

Lead-authored-by: Tadeja Kadunc <tadeja.kadunc@gmail.com>
Co-authored-by: tadeja <tadeja@users.noreply.github.com>
Co-authored-by: Alenka Frim <AlenkaF@users.noreply.github.com>
Signed-off-by: AlenkaF <frim.alenka@gmail.com>