Make the Settings Model tests into proper CI tests

[DHowett]

This pull request removes the need for the SettingsModel tests to run in
a UAP harness and puts them into the standard CI rotation.

This required some changes to Run-Tests.ps1 to ensure that the right
te.exe is selected for each test harness. It's a bit annoying, but for
things that depend on a resources.pri, that file must be in the same
directory as the EXE that is hosting the test. Not the DLL, mind you,
the EXE. In our case, that's TE.ProcessHost.exe

The bulk of the change is honestly namespace tidying.

[DHowett]

It is important to note that these tests currently fail, because one of the profile tests has been broken since #15843 (very recently! this PR will prevent future regressions!) and one is broken on the test agent due to long file paths. Ha.

[zadjii-msft]

now if only this worked with the TerminalApp ones too, oh man would that be sweet

[DHowett]

I'd like to merge these green :)

@zadjii-msft would you be able to look into the profile icon failure?

@lhecker would you mind looking at the commandline normalization failure? We have seen smth like this before

[lhecker]

expected: C:\Users\SHINET~1\AppData\Local\Temp\be8dba0d-abb9-45b0-b352-cdf6dea84b45 two\file 2.exe
actual: C:\Users\ShineTest\AppData\Local\Temp\be8dba0d-abb9-45b0-b352-cdf6dea84b45 two\file 2.exe

The good news is that the path normalization worked! The bad news is that the CI's username is too long.

[DHowett]

@lhecker yay! that worked! Now it's just Mike's 🥲

[zadjii-msft]

Done. I absolutely adore that these can run in CI now