Add a warning when the user sets their colorScheme to a scheme that doesn't exist. When that occurs, we'll set their color table to the campbell scheme, to prevent it from being just entirely black.
This commit also switches scheme storage to a map keyed on name.
Closes#2547
* Warn the user when their settings are bad
The start of work on #1348
* Display an error dialog for errors during validation
* Polish for PR
* Add a ton of tests
* Polish the _GetMessageText bits
* Add code to check for duplicate profiles
* Verify that many warnings work at the same time
* comments y'all
* Apply fixes for dustin's thoughts from PR
* Add a proper exception type, use an array instead of a map
* PR Fixes
* Fix x86 build break
* Add a bit on "using the defaults" when we encountering an exception
* remove a redundant variable
* guid->GUID
* Address Michael's PR comments
* Clean up this error text, and catch exceptions better
* Update src/cascadia/TerminalApp/Resources/en-US/Resources.resw