[llvm] [offload] Decouple PluginManager from the OpenMP offload policy handling (PR #208113)

[Ivan R. Ivanov via llvm-commits]

https://github.com/ivanradanov commented:

You are correct in your assumption that the existing `libomptarget` ABI will remain stable. I do not intend to make _any_ ABI changes to it and the `__tgt_rtl_init` was an exception because it is only used in testing.

Tangentially, regarding `libomptarget` I actually think we should version the libraries and explicitly disallow linking a different LLVM major version `libomptarget` from the compiler because even though the ABI is the same I find it it often breaks due to implementation changes but that's a different topic.

https://github.com/llvm/llvm-project/pull/208113