Remove RTTI from the Tensor API. Refactor operation handling in the graph.

Remove virtual inheritance from the operation implementations and stop using
side-casting using `dynamic_cast` to find out if an operation is implemented by
a backend.

Add a list of "graph::BackendExtension" elements that can be grafted onto an
operation. Backends implementation of every operation are now implemented by
deriving from this new class. When lowering to a specific backend, we go
through the list of extensions attached to an operation to find a matching
backend.

Backend identification is done by calling `BackendExtension::GetTypeId()`.

As a result of the above changes, operation node implementations don't need to
be defined as templates anymore.

PiperOrigin-RevId: 914983314

Author: qukhan

BUILD.gn

@@ -360,6 +360,20 @@ xnnpack_source_set("operators") {
   }
 }
 
+xnnpack_source_set("subgraph_matchers") {
+  sources = [
+    "test/subgraph/rewrites/subgraph_matcher.cc",
+    "test/subgraph/rewrites/subgraph_matcher.h",
+  ]
+
+  public_deps = [
+    ":xnnpack_headers",
+    "//third_party/googletest:gtest",
+  ]
+
+  testonly = true
+}
+
 xnnpack_source_set("subgraph") {
   deps = [
     ":microkernel_headers",

litert/tensor/BUILD

@@ -47,6 +47,7 @@ cc_library(
     # copybara:uncomment includes = ["utils"],
     deps = [
         "//litert/tensor:datatypes",
+        "//litert/tensor/internal:type_id",
         "@abseil-cpp//absl/status",
         "@abseil-cpp//absl/status:statusor",
         "@abseil-cpp//absl/types:span",
@@ -89,7 +90,6 @@ cc_library(
     deps = [
         "//litert/tensor:datatypes",
         "//litert/tensor/internal:graph",
-        "//litert/tensor/internal:mixin",
         "@abseil-cpp//absl/strings:string_view",
     ],
 )