Consolidate platform and adapter backend enums into one. (#17605)

second attempt to land intel/llvm#16173

Author: aarongreig

examples/codegen/codegen.cpp

@@ -49,11 +49,11 @@ std::vector<ur_adapter_handle_t>
 get_supported_adapters(std::vector<ur_adapter_handle_t> &adapters) {
   std::vector<ur_adapter_handle_t> supported_adapters;
   for (auto adapter : adapters) {
-    ur_adapter_backend_t backend;
+    ur_backend_t backend;
     ur_check(urAdapterGetInfo(adapter, UR_ADAPTER_INFO_BACKEND,
-                              sizeof(ur_adapter_backend_t), &backend, nullptr));
+                              sizeof(ur_backend_t), &backend, nullptr));
 
-    if (backend == UR_ADAPTER_BACKEND_LEVEL_ZERO) {
+    if (backend == UR_BACKEND_LEVEL_ZERO) {
       supported_adapters.push_back(adapter);
     }
   }

include/ur_api.h

@@ -838,8 +838,8 @@ namespace ur {
 * A manifest requires the following scalar fields: {`name`, `backend`}
   - `name` must be a string unique to the adapter.
   - `name` should be identical to how the name appears in the adapter's library name. E.g. `libur_adapter_my_adapter` should have the name string `my_adapter`.
-  - `backend` must be an etor of `$x_adapter_backend_t`.
-  - `backend` must not be `$X_ADAPTER_BACKEND_UNKNOWN`.
+  - `backend` must be an etor of `$x_backend_t`.
+  - `backend` must not be `$X_BACKEND_UNKNOWN`.
 * a manifest requires the following sequence of scalars: {`device_types`}
   - `device_types` must be an etor of `$x_device_type_t`
 

include/ur_print.h

@@ -133,7 +133,7 @@ name: $x_adapter_info_t
 typed_etors: True
 etors:
     - name: BACKEND
-      desc: "[$x_adapter_backend_t] Identifies the native backend supported by the adapter."
+      desc: "[$x_backend_t] Identifies the native backend supported by the adapter."
     - name: REFERENCE_COUNT
       desc: |
             [uint32_t] Reference count of the adapter.
@@ -187,30 +187,6 @@ returns:
     - $X_RESULT_ERROR_OUT_OF_HOST_MEMORY
 --- #--------------------------------------------------------------------------
 type: enum
-desc: "Identifies backend of the adapter"
-class: $x
-name: $x_adapter_backend_t
-etors:
-    - name: UNKNOWN
-      value: "0"
-      desc: "The backend is not a recognized one"
-    - name: LEVEL_ZERO
-      value: "1"
-      desc: "The backend is Level Zero"
-    - name: OPENCL
-      value: "2"
-      desc: "The backend is OpenCL"
-    - name: CUDA
-      value: "3"
-      desc: "The backend is CUDA"
-    - name: HIP
-      value: "4"
-      desc: "The backend is HIP"
-    - name: NATIVE_CPU
-      value: "5"
-      desc: "The backend is Native CPU"
---- #--------------------------------------------------------------------------
-type: enum
 desc: "Minimum level of messages to be processed by the logger."
 class: $xAdapter
 name: $x_logger_level_t