This ensures we run in a clean directory, using our real distribution. It finds bugs like @internal
APIs needed to type-check in the offline compiler, as well as problems in package.json.
Also move tsc-wrapped under tools/@angular
This symbol is no longer reexported at the top level, so it's safe to not mark it as internal.
This fixes the offline compilation which got broken by this symbol not being present in the d.ts
files when the compiler tries to do a deep import.
Closes#8819