[UR][L0] Add read-only flag to host memory registration
Replace the placeholder TBD flag in the host memory registration flags enum
with UR_EXP_USM_HOST_ALLOC_REGISTER_FLAG_READ_ONLY and regenerate the API
headers. The flag indicates that device access to the registered range is
read-only.
In the Level Zero v2 adapter, map the flag onto
ZE_HOST_MEM_ALLOC_FLAG_MEM_READ_ONLY when calling zeMemAllocHost so the
driver registers the external system memory range in read-only device-access
mode.
Assisted-By: Claude
