[OpenMP] Replace GPU globalization calls with shared memory in the middle-end

Summary:
The changes introduced in D97680 create a simpler interface to code that needs
to be globalized. This interface is used to simplify the globalization calls in
the middle end. We can check any globalization call that is only called by a
single thread in the team and replace it with a static shared memory buffer.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D97818