Add actions missing in schema, descriptions for toggleRetroEffect

[zadjii-msft]

Summary of the Pull Request

In the wake of #6635, a couple things got missed in merges:

• toggleRetroEffect didn't get into the schema, nor did renameTab or
  commandPalette.
• toggleRetroEffect also didn't get a name

Furthermore, I thought it might be a good idea to start sticking
commands into bindings even without keys. So I tried doing that for
opentabColorPicker and toggleRetroEffect, and found immediately that
the labels for the key chord still appear even when the text is empty.
So I added some XAML magic to hide those when the text is empty.

References

• Add toggleRetroEffect to schema #6762
• Add a ShortcutAction for toggling retro terminal effect #6691
• Add keybinding to rename tab #6557
• Add support for the Command Palette #6635

PR Checklist

• Closes Add toggleRetroEffect to schema #6762
• I work here
• Tests added/passed
• [n/a] Requires documentation to be updated

Detailed Description of the Pull Request / Additional comments

• See also: https://docs.microsoft.com/en-us/windows/uwp/data-binding/data-binding-quickstart#formatting-or-converting-data-values-for-display
  • make sure to switch to C++/WinRT at the top!

Validation Steps Performed

Removed all my manual actions, ran the Terminal:

[DHowett]

This value converter! I love it!

[DHowett]

/cc @leonMSFT for some more xaml magic

[leonMSFT]

wtf that's so neat

[ghost]

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