Modernize Lib/test/test_decimal.py: use argparse instead of optparse

[tonghuaroot]

Feature or enhancement

Proposal:

Description

Lib/test/test_decimal.py currently uses the deprecated optparse module for parsing command-line arguments. This task involves migrating it to use argparse.

Proposed Changes

• Replace optparse imports with argparse.
• Update argument parsing logic to use argparse.ArgumentParser.
• Ensure all existing command-line options (--debug, --skip) are supported.
• Fix any formatting issues (e.g. % in help strings).

Verification

• Run python Lib/test/test_decimal.py --help
• Run python Lib/test/test_decimal.py --skip

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-143984: Replace optparse with argparse in Lib/test/test_decimal.py #143983

[tanloong]

The optparse module was actually undeprecated (see #126180) after some discussion about its continued value.