[OpenMP][OpenMPIRBuilder] Migrate OffloadEntriesInfoManager from clang to OMPIRbuilder

This patch moves the implementation of the OffloadEntriesInfoManager
to the OMPIRbuilder. This class will later be used by flang as well.

    Reviewed By: jdoerfert

    Differential Revision: https://reviews.llvm.org/D135786