[Enterprise, GPO] Add "Default Terminal app" policy to definition template

[htcfreek]

Summary of the Pull Request

This PR implements a policy definition for setting/enforcing the default terminal application.

References and Relevant Issues

GitHub (issues):

• Group Policy to control default Terminal setting #18302
• Group Policy to control default Terminal setting #18303

Docs:

• https://support.microsoft.com/en-us/windows/command-prompt-and-windows-powershell-for-windows-11-6453ce98-da91-476f-8651-5c14d5777c20
• Does Windows 10 support setting Terminal as the default console host? #13153 (comment)

Detailed Description of the Pull Request / Additional comments

This PR adds a new policy definition to the ADMX templates for settings the default Terminal application in Windows.

Note

This PR does not change any code of Windows, Console Host or WIndows Terminal. It only adds the definiton for a new policy to the templates.

I got the registry values form the documentation and by testing the values.

The policy is only available as user policy because the registry values have to be in HKCU.

The Policy is implemented as preference (not inside the Policy key) and therefore keeps it's value on removing (not configured) it. You can see this in gpedit.msc on the policy symbol and the hint in the description.

Validation Steps Performed

Manual testing the policy.

PR Checklist

• Closes Group Policy to control default Terminal setting #18302
• Tests added/passed
• Documentation updated
  • If checked, please file a pull request on our docs repo and link it here: [GroupPolicy docs] Add new "Default Terminal Application" policy MicrosoftDocs/terminal#823
• Schema updated (if necessary)

[htcfreek]

Can you please assign me.

[htcfreek]

/azp run

[azure-pipelines]

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