[LOADER] Added Prefilter using ONEAPI_DEVICE_SELECTOR to remove backends

[nrspruit]

• Added Prefilter which uses ONEAPI_DEVICE_SELECTOR to remove backends that the user has not requested.
• this handles both the "Accept" or "Discard" filters that can be set in the ONEAPI_DEVICE_SELECTOR.
• Added tests verify the Accept/Discard use cases on Linux.
• Added UR_LOADER_PRELOAD_FILTER to toggle the prefilter on and off.

[pbalcer]

lgtm, just a few nits.

[pbalcer]

L0 e2e fails with:

  SYCL :: Basic/accessor/accessor.cpp
  SYCL :: DeviceArchitecture/device_architecture_comparison_on_device_aot.cpp
  SYCL :: ESIMD/grf.cpp
  SYCL :: Graph/Explicit/interop-level-zero-launch-kernel.cpp
  SYCL :: Graph/RecordReplay/interop-level-zero-launch-kernel.cpp
  SYCL :: syclcompat/launch/launch_policy_lmem.cpp

However, the exact same of tests are failing on main:

  SYCL :: Basic/accessor/accessor.cpp
  SYCL :: DeviceArchitecture/device_architecture_comparison_on_device_aot.cpp
  SYCL :: ESIMD/grf.cpp
  SYCL :: Graph/Explicit/interop-level-zero-launch-kernel.cpp
  SYCL :: Graph/RecordReplay/interop-level-zero-launch-kernel.cpp
  SYCL :: syclcompat/launch/launch_policy_lmem.cpp

So seems unrelated.

[pbalcer]

I'll merge once CI completes.