[Specialized Kernel] Update yaml syntax to use kernel instead of dispatch (#104070)

Based on this [code search](https://fburl.com/code/gjcnw8ly) (*.yaml with `dispatch: CPU:`), update all files found to use

```
kernels:
    - arg_meta: None
      kernel_name:
```
instead of
```
dispatch:
    CPU:
```
---
## Code changes:

- `fbcode/executorch/codegen/tools/gen_oplist.py`
  - Strip ET specific fields prior to calling parse_native_yaml_struct
---
## Files edited that are not `*functions.yaml` or `custom_ops.yaml`

- fbcode/executorch/kernels/optimized/optimized.yaml
- fbcode/executorch/kernels/quantized/quantized.yaml
- fbcode/executorch/kernels/test/custom_kernel_example/my_functions.yaml

---
## Found Files that were not edited

**Dispatched to more than just CPU**
- fbcode/caffe2/aten/src/ATen/native/native_functions.yaml
- xplat/caffe2/aten/src/ATen/native/native_functions.yaml
- xros/third-party/caffe2/caffe2/aten/src/ATen/native/native_functions.yaml

**Grouped ops.yaml path**
- fbcode/on_device_ai/Assistant/Jarvis/min_runtime/operators/ops.yaml

---
**Design Doc:** https://docs.google.com/document/d/1gq4Wz2R6verKJ2EFseLyPdAF0wqomnCrVDDJpRkYsRw/edit?kh_source=GDOCS#heading=h.8raqyft9y50

Differential Revision: [D46952067](https://our.internmc.facebook.com/intern/diff/D46952067/)

**NOTE FOR REVIEWERS**: This PR has internal Meta-specific changes or comments, please review them on [Phabricator](https://our.internmc.facebook.com/intern/diff/D46952067/)!
Pull Request resolved: #104070
Approved by: https://github.com/larryliu0820

Author: Jack-Khuu

test/edge/custom_ops.yaml

@@ -1,3 +1,4 @@
 - func: custom::add_3.out(Tensor a, Tensor b, Tensor c, *, Tensor(a!) out) -> Tensor(a!)
-  dispatch:
-    CPU: custom::add_3_out
+  kernels:
+    - arg_meta: null
+      kernel_name: custom::add_3_out

torchgen/executorch/parse.py

@@ -130,9 +130,7 @@ def parse_et_yaml(
     et_kernel = extract_kernel_fields(es)
 
     # Remove ET specific fields from entries for BC compatibility
-    for entry in es:
-        for field in ET_FIELDS:
-            entry.pop(field, None)
+    strip_et_fields(es)
 
     native_yaml = parse_native_yaml(
         path,
@@ -142,3 +140,12 @@ def parse_et_yaml(
         loaded_yaml=es,
     )
     return native_yaml.native_functions, et_kernel
+
+
+def strip_et_fields(es: object) -> None:
+    """Given a loaded yaml representing a list of operators,
+    remove ET specific fields from every entries for BC compatibility
+    """
+    for entry in es:  # type: ignore[attr-defined]
+        for field in ET_FIELDS:
+            entry.pop(field, None)