If we're creating a universal app, and here are satellite assemblies that are not
identical across all RuntimeIdentifiers, those assemblies will be stored in a RuntimeIdentifier-specific
subdirectory during the build.
Unfortunately we didn't know how to find those assemblies at runtime, causing localizations
in universal apps to not work.
This change will:
* Add support for looking in the directory where RID-specific satellite assemblies
are stored.
* Add an assembly resolution event handler to our CoreCLR bridge so that we can
execute our custom lookup code.
* Add an assembly resource lookup test to monotouch-test.
* Add a macOS + Mac Catalyst variation of monotouch-test to xharness that triggers
the bug (a universal test app).
Fixes https://github.com/xamarin/xamarin-macios/issues/16847.
Rolf Bjarne Kvinge