[OpenMP][OMPIRBuilder] Make OffloadEntriesInfoManager a member of OpenMPIRBuilder

This patch adds the OffloadEntriesInfoManager to the OpenMPIRBuilder, and
allows the OffloadEntriesInfoManager to access the Configuration in the
OpenMPIRBuilder.  With the shared Config there is no risk for inconsistencies,
and there is no longer the need for clang to have a separate
OffloadEntriesInfoManager.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D146549