Migrate gen_oplist.py to use executorch/codegen instead of pytorch torchgen (#11104)

Summary: As titled, after #10939 we are able to use `executorch.codegen` APIs instead of `torchgen.executorch` APIs. This PR moves `gen_oplist.py` to use the new `executorch.codgen` API.

Differential Revision: D75307480

Pulled By: larryliu0820

Author: larryliu0820

codegen/parse.py

@@ -4,8 +4,12 @@
 from typing import Any
 
 import yaml
-
-from executorch.codegen.model import ETKernelIndex, ETKernelKey
+try:
+    from executorch.codegen.model import ETKernelIndex, ETKernelKey
+except ImportError:
+    # If we build from source, executorch.codegen is not available.
+    # We can use relative import instead.
+    from .model import ETKernelIndex, ETKernelKey
 from torchgen.gen import LineLoader, parse_native_yaml
 from torchgen.model import (
     BackendMetadata,

codegen/tools/gen_oplist.py

@@ -12,7 +12,12 @@
 from typing import Any, Dict, List, Optional, Set
 
 import yaml
-from torchgen.executorch.parse import strip_et_fields
+try:
+    from executorch.codegen.parse import strip_et_fields
+except ImportError:
+    # If we build from source, executorch.codegen is not available.
+    # We can use relative import instead.
+    from ..parse import strip_et_fields
 
 from torchgen.gen import LineLoader, parse_native_yaml_struct
 from torchgen.selective_build.operator import SelectiveBuildOperator

codegen/tools/targets.bzl

@@ -15,8 +15,9 @@ def define_common_targets(is_fbcode = False):
         visibility = [
             "//executorch/...",
         ],
-        external_deps = ["torchgen"],
-        deps = select({
+        deps = [
+            "//executorch/codegen:gen_lib",
+        ] + select({
             "DEFAULT": [],
             "ovr_config//os:linux": [] if runtime.is_oss else ["//executorch/codegen/tools/fb:selective_build"],  # TODO(larryliu0820) :selective_build doesn't build in OSS yet
         }),