[PassBuilder] Add OpenMPOpt to default LTO pipeline

The LTO support for OpenMP offloading allows us to run the OpenMPOpt
pass during the LTO pipeline. This patch introduces an early run of the
Module pass and a late run of the CGSCC pass. These are quick no-ops if
there is no OpenMP in the module.

Depends on D118198

Differential Revision: https://reviews.llvm.org/D118611