Review and simplify argparse docs #124478

The argparse docs have become pretty lengthy. This is in part due to the examples, which are somewhat duplicative of the tutorial. I'd like to go through the docs to see if we can dedupe and pare things down to make them more readable.

Linked PRs

• GH-124478: Cleanup argparse documentation #124877
• [3.13] GH-124478: Cleanup argparse documentation (GH-124877) #125162
• [3.12] GH-124478: Cleanup argparse documentation (GH-124877) #125164