gh-126180: Remove getopt and optparse deprecation notices (GH-126227)

* Remove getopt and optparse deprecation notices
* Add new docs sections for command line app helper libraries
* Add guidance on choosing a CLI parsing library to the optparse docs
* Link to the new guidance from the argparse and getopt docs
* Reword intro in docs section for superseded stdlib modules
* Reframe the optparse->argparse guide as a migration guide
  rather than as an upgrade guide

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Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>