Convert TerminalSettingsEditor into a DLL

[leonMSFT]

This PR's only purpose is to convert the TSE project into a DLL while getting rid of unnecessary files in the meantime, namely the App.* files and moving its ResourceDictionary into a file called CommonResources.xaml.

In the process, I needed to move all the Model classes under Editor since it would have been a huge pain to try to add a Model dll alongside the Editor dll. I figured it also wouldn't matter too much since we'll be deleting the Model namespace in favor of using the incoming TSM.

While this doesn't contain any code of putting the Settings UI in a tab, I figured it would be nice to push this particular part as its own standalone PR.

[DHowett]

(That's the extent of my review.)

[carlos-zamora]

A part of me doesn't like that you replaced Microsoft.Terminal.Settings.Model references with Microsoft.Terminal.Settings.Editor.Model, even though I know they'll be replaced soon. Any way you can keep them as it was before? If it's too much work, I'll give up on this one.

Also want to see if we can rename the dll.

[leonMSFT]

Yeah I don't like it either 😢, I still don't think it's worth the effort to keep it as .Settings.Model, especially since it's gonna be replaced soon.

It looks like to rename the dll, changing <ProjectName> was sufficient, but it left a wacky residual empty Microsoft.Terminal.Settings.Editor folder, and the guts were all in a TerminalSettingsEditor folder. I fixed it by changing the vcxproj name as well, and along with that the references to the vcxprojs in OpenConsole.sln and other vcxprojs.

[carlos-zamora]

\azp run

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