Collect all known PowerShell Core installations for dynamic profiles (#4273)

This pull request teaches the PowerShell Core generator about a bunch of different locations in which it might find a PowerShell.

These instances will be sorted, a leader will be elected, and that leader will be promoted and given the vaunted title of "PowerShell".

Names will be generated for the rest.

The sort order is documented in the comments, but that comment will be replicated here:

```
// <-- Less Valued .................................... More Valued -->
// |                 All instances of PS 6                 | All PS7  |
// |          Preview          |          Stable           | ~~~      |
// |  Non-Native | Native      |  Non-Native | Native      | ~~~      |
// | Trd  | Pack | Trd  | Pack | Trd  | Pack | Trd  | Pack | ~~~      |
// (where Pack is a stand-in for store, scoop, dotnet, though they have their own orders,
// and Trd is a stand-in for "Traditional" (Program Files))
```

Closes #2300

Author: DHowett

src/cascadia/CascadiaPackage/ProfileIcons/pwsh-preview.scale-100.png

@@ -28,9 +28,5 @@ namespace TerminalApp
         std::wstring_view GetNamespace() override;
 
         std::vector<TerminalApp::Profile> GenerateProfiles() override;
-
-    private:
-        static bool _isPowerShellCoreInstalled(std::filesystem::path& cmdline);
-        static bool _isPowerShellCoreInstalledInPath(const std::wstring_view programFileEnv, std::filesystem::path& cmdline);
     };
 };