Add icon override setting for newTabMenu entries

[GeekJosh]

Summary of the Pull Request

This PR is to allow users to set a custom icon for entries in the new tab menu for "action" and "profile" type entries.

References and Relevant Issues

This PR is in response to #18103

Detailed Description of the Pull Request / Additional comments

It is now possible to specify an optional "icon" setting for any "action" or "profile" type entry in the "newTabMenu" JSON settings. When specified, this icon will be used as the menu icon for that action/profile in the new tab menu. If not specified, the action/profile definition's default icon will be used instead (if present).

The Cascadia settings schema ("doc/cascadia/profiles.schema.json") has been updated to reflect this.

Validation Steps Performed

Manually tested with multiple combinations of icon settings:

• ActionEntry:
  • valid path in action definition and new tab entry (renders new tab entry icon)
  • valid path in action definition but no path in new tab entry (renders action definition icon)
  • no path in action definition, valid path in new tab entry (renders new tab entry icon)
  • invalid path in action definition, valid path in new tab entry (renders new tab entry icon)
  • valid path in action definition, invalid path in new tab entry (renders no icon)
  • invalid path in both (renders no icon)
  • no path in both (renders no icon)
• ProfileEntry:
  • valid path in new tab entry (renders new tab entry icon)
  • no path in new tab entry (renders profile's default icon)
  • invalid path in new tab entry (renders no icon)

PR Checklist

• Closes In newTabMenu allow assignment/override of the icon property for the action items #18103
• Tests added/passed
• Documentation updated
  • If checked, please file a pull request on our docs repo and link it here: #808
• Schema updated (if necessary)

[GeekJosh]

@GeekJosh please read the following Contributor License Agreement(CLA). If you agree with the CLA, please reply with the following information.

@microsoft-github-policy-service agree [company="{your company}"]

Options:

• (default - no company specified) I have sole ownership of intellectual property rights to my Submissions and I am not making Submissions in the course of work for my employer.

@microsoft-github-policy-service agree

• (when company given) I am making Submissions in the course of work for my employer (or my employer has intellectual property rights in my Submissions by contract or applicable law). I have permission from my employer to make Submissions and enter into this Agreement on behalf of my employer. By signing below, the defined term “You” includes me and my employer.

@microsoft-github-policy-service agree company="Microsoft"

Contributor License Agreement

@microsoft-github-policy-service agree

[DHowett]

oh, I think I need to comment here before it will run pipelines now. FLY, MY PRETTIES

[DHowett]

Thank you so much - this is excellent work! Exactly what we needed.

[carlos-zamora]

This is great! Thank you!