Add the 'SelectCommandArgument' bind-able function

[daxian-dbw]

PR Summary

Add the SelectCommandArgument bind-able function.
This functionality was originally proposed by @ThePSAdmin who added a argument selection handler to SamplePSReadLineProfile.ps1 via #1947. This PR adds a built-in function for this functionality with improvements.

Improvements:

1. Selection of arguments is scoped in script blocks. Based on the cursor position, it searches from the most nested script block to the outmost script block. This offers better user experience when looping through arguments.
2. When the cursor is at an argument, Ctrl+a selects that specific argument.
3. Improve the digit arguments handling to treat the positive/negative argument value as a forward/backward offset from the currently selected argument or the current cursor position when no argument is selected.
4. Some minor fixes and add a lot tests.

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure you've added one or more new tests
• Make sure you've tested these changes in terminals that PowerShell is commonly used in (i.e. conhost.exe, Windows Terminal, Visual Studio Code Integrated Terminal, etc.)
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed at PowerShell-Docs
    • Doc Issue filed: Update PSReadLine doc for the new function 'SelectCommandArgument' MicrosoftDocs/PowerShell-Docs#7259

Microsoft Reviewers: Open in CodeFlow

[ghost]

🎉 v2.2.0-beta2 has been released which incorporates this pull request. 🎉