After a header is renamed that is used in a source, the IntelliSense squiggles don't update to reflect the change. In some cases, the even editing/save the file doesn't pick up the changes from the rename, i.e. the file in the #include <> no longer exists, but IntelliSense doesn't complain about it -- it seems like it's using some cached version of the non-existent file.

I hit this while doing the repro of #3378 and renaming headers_test.h.

So this might be 2 bugs:

1. The rename should auto-trigger an update squiggles without having to edit/save (i.e. non-existent file becomes existent).
2. The rename should clear the IntelliSense process cache of the file if the file doesn't exist any more.