[OpenMP][libomptarget] Improving plugin resource managers

This patch improves the resource managers in the plugins by properly handling
the errors. Until now, errors when creating and destroying resources were not
propagated and were directly handled inside the resource managers. Now, all
errors are propagated as in the rest of the plugin infrastructure.

The code is now ready to implement the request/return of multiple resources in
a single getResource/returnResource call.

Differential Revision: https://reviews.llvm.org/D155621