Improve help text output by the default help subcommand

[rgoldberg]

The help text output by the default help subcommand doesn't seem proper to me:

1. The USAGE section doesn't show -h, --help, or --version if they are autogenerated
2. The USAGE section doesn't indicate that <subcommand> is optional, or that it can be followed by additional arguments
3. The OPTIONS section lists --version before -h, --help, but I think they should be sorted alphabetically
4. The SUBCOMMANDS section doesn't show help … Show help information., which I think should be inserted alphabetically in the subcommand list

ArgumentParser version:

main

Swift version: Paste the output of swift --version here.

swift-driver version: 1.127.14.1 Apple Swift version 6.2.1 (swiftlang-6.2.1.4.8 clang-1700.4.4.1)
Target: arm64-apple-macosx26.0

Checklist

• If possible, I've reproduced the issue using the main branch of this package
• I've searched for existing GitHub issues

Steps to Reproduce

Run the help subcommand of a command that has both a default help subcommand and that has CommandConfiguration.version set. They needn't exist together, but doing this shows both problems at once.

Expected behavior

Top-level help output:

OVERVIEW: Command

USAGE: cmd [(-h | --help) [<subcommand>] | --version | <subcommand> *…]

OPTIONS:
  -h, --help              Show help information.
  --version               Show the version.

SUBCOMMANDS:
  a                       A
  b                       B
  c                       C
  help                    Show help information.

Actual behavior

Top-level help output:

OVERVIEW: Command

USAGE: cmd <subcommand>

OPTIONS:
  --version               Show the version.
  -h, --help              Show help information.

SUBCOMMANDS:
  a                       A
  b                       B
  c                       C