feat(getopt): Support option terminator (--)

[lewis-yeung]

Description

Support the option terminator -- in getopt, which is compatible with POSIX conventions for command line options (see reference for details).

Motivation and Context

This is also a prerequisite for fixing #5094.

How Has This Been Tested?

Tested locally with updated test/Scoop-GetOpts.Tests.ps1. All passed.

Checklist:

• I have read the Contributing Guide.
• I have ensured that I am targeting the develop branch.
• I have updated the documentation accordingly.
• I have updated the tests accordingly.
• I have added an entry in the CHANGELOG.

[niheaven]

I've gotten it nearly in the same way, but the question is, PowerShell won't pass -- in its subprocess, so you canot get this -- in subcommand. A -- support in getopt has nothing to do with the bug.

[lewis-yeung]

but the question is, PowerShell won't pass -- in its subprocess, so you canot get this -- in subcommand. A -- support in getopt has nothing to do with the bug.

@niheaven We can pass '--' which is treated as a string in PowerShell. After all, it's impossible to use -- directly in PowerShell CLI.

[niheaven]

LGTM, now could move on.