gh-148468: Accept string-like help proxies in argparse

[RaghunandanKumar]

Summary

• restore support for string-like proxy objects in colorized argparse descriptions, epilogs, and argument help text
• normalize formatter text at the string-formatting boundary instead of assuming concrete str objects
• add regression coverage for proxied descriptions, epilogs, and interpolated help text

Issue

• Cannot use lazy translation proxies in argparse help #148468

Testing

• ./python.exe -m test test_argparse
• runtime repro with a minimal LazyStr proxy and parser.format_help()