#### ⚠️ This targets #10051
## Summary of the Pull Request
This PR creates a `Samples` solution which can be used for quickly testing our particular WinUI + Xaml Islands + wapproj setup, with a `TermControl`. This lets us quickly prototype and minimally repro xaml islands bugs, but also lets us iterate quickly on changes in the process model. I'll be using this in the future to prove that the out-of-proc control works (for tear-out), without having to tear up the entire `TerminalApp` all at once.
While I'll be leaning on this extensively for tear-out prototyping, I've also found myself wanting this kind of sample sln many times in the past. We run into bugs all the time where we're not sure if they're XAML Islands bugs or Terminal bugs. However, standing up a scratch sln with MUX hooked up, and a `XamlApplication` from the toolkit, and XAML Islands is time consuming. This sample sln should let us validate if bugs are XI bugs or Terminal bugs much easier.
## References
* Tear-out: #1256
* Megathread: #5000
* Project: https://github.com/microsoft/terminal/projects/5
## PR Checklist
* [x] Closes one bullet point of https://github.com/microsoft/terminal/projects/5#card-50760312
* [x] I work here
* [x] Tests added/passed
* [n/a] Requires documentation to be updated
## Detailed Description of the Pull Request / Additional comments
This is _largely_ a copy-pasta of our existing projects, in massively simplified form. I'm gonna wontfix most comments on the code that was copy-pasta'd. If it's bad here, it's probably also bad in the real version in `OpenConsole.sln`.
* I made an entirely new `.sln` for this, so that these samples wouldn't need to build in CI. They're not critical code, they're literally just for prototyping.
* `TerminalAppLib` & `TerminalApp` became `SampleAppLib` and `SampleApp`. This is just a simple application hosting a single `TermControl`. It references the winmds and dlls from the main `OpenConsole.sln`, but in a way that would be more like a project consuming a nuget feed of the control, rather than a `ProjectReference`.
- It still does all the `App.xaml` and `Toolkit.XamlApplication` stuff that TerminalApp does, so that it can load MUX resources, and do MUX-y things.
* `WindowsTerminal` became `WindowExe`. I tore out all of the `NonClientIslandWindow` stuff - this is just a window with a xaml island.
* `CascadiaPackage` became `Package`. It does the vclibs hack again for the `TerminalConnection` dlls (because this package can't actually determine that `TerminalConnection.dll` requires `cprest*.dll`), as well as for `windowsterminal.exe` (which we'll need in the future for out-of-proc controls). I got rid of all the Dev/Preview/Release asset machinations as well.
Wherever possible, I changed filenames slightly so that they won't get accitdentally opened when someone tries to open a file by name in their editor (**cough** sublime's <kbd>ctrl+p</kbd> menu **cough**).
## Validation Steps Performed
The sample app launches, and displays a TermControl. What else do you want? <sup>(_rhetorical, not a prompt for a wishlist_)</sup>
(cherry picked from commit 30d6cf4839fca8ac8203f6c2489b02a4088b851e)
Mike Griese