Update on "[kernel] Add template based unboxing"

Adding a new feature to allow users to bypass codegen and register their
kernels directly. This is very useful for custom kernels for custom ops.

Example usage:
```
Tensor& my_op(RuntimeContext& ctx, const Tensor& self, const Tensor& other, Tensor& out) {
    // ...
    return out;
}

Kernel my_kernel = Kernel.make_boxed_kernel("my_ns::my_op",EXECUTORCH_FN(my_op));

register_kernels({my_kernel});
```

Differential Revision: [D51553099](https://our.internmc.facebook.com/intern/diff/D51553099)

[ghstack-poisoned]

Author: larryliu0820

runtime/kernel/test/make_boxed_from_unboxed_functor_test.cpp

@@ -40,7 +40,7 @@ TEST_F(MakeBoxedFromUnboxedFunctorTest, Basic) {
   Kernel my_kernel =
       Kernel::make_boxed_kernel("my_ns::my_op.out", EXECUTORCH_FN(my_op_out));
   ArrayRef<Kernel> kernels_array = ArrayRef<Kernel>(my_kernel);
-  // patternlint-disable-next-line clang-diagnostic-unused-variable
+  // @lint-ignore CLANGTIDY
   auto s1 = register_kernels(kernels_array);
   EXPECT_TRUE(hasOpsFn("my_ns::my_op.out"));
 }
@@ -49,7 +49,7 @@ TEST_F(MakeBoxedFromUnboxedFunctorTest, UnboxLogicWorks) {
   Kernel my_kernel =
       Kernel::make_boxed_kernel("my_ns::set_1.out", EXECUTORCH_FN(set_1_out));
   ArrayRef<Kernel> kernels_array = ArrayRef<Kernel>(my_kernel);
-  // patternlint-disable-next-line clang-diagnostic-unused-variable
+  // @lint-ignore CLANGTIDY
   auto s1 = register_kernels(kernels_array);
   EXPECT_TRUE(hasOpsFn("my_ns::set_1.out"));