[7/N] Add sugar syntax for module.update

The update API in method is supposed to be portable, but we can make it more user friendly for the update API in module. Add a bit sugar syntax in module to improve UX. Such that user can update backend option in module like following:
```
Module module(stub_model_path_);
int new_num_threads = 4;

const auto update_result = module.update("forward",
      {
        {"StubBackend", {{IntKey("NumberOfThreads"), new_num_threads}}
      },
  );
```

Differential Revision: [D76242292](https://our.internmc.facebook.com/intern/diff/D76242292/)

[ghstack-poisoned]

Author: cccclai

extension/module/dynamic_backend_options_map.h

@@ -0,0 +1,43 @@
+
+#pragma once
+
+#include <vector>
+#include <string>
+#include <initializer_list>
+#include <executorch/runtime/backend/backend_options.h>
+
+namespace executorch {
+namespace runtime {
+
+class DynamicBackendOptionsMap {
+ public:
+  using OptionList = std::initializer_list<BackendOption>;
+
+  DynamicBackendOptionsMap(
+      std::initializer_list<std::pair<const char*, OptionList>> list) {
+    entries_.reserve(list.size());
+    for (const auto& item : list) {
+      // Store backend name
+      backend_names_.push_back(item.first);
+      // Store options
+      options_storage_.push_back(std::vector<BackendOption>(item.second));
+      // Create Entry with stable references
+      entries_.push_back({
+          backend_names_.back().c_str(),
+          ArrayRef<BackendOption>(options_storage_.back().data(), options_storage_.back().size())
+      });
+    }
+  }
+
+  ArrayRef<Entry> entries() const {
+    return ArrayRef<Entry>(entries_.data(), entries_.size());
+  }
+
+ private:
+  std::vector<std::string> backend_names_;
+  std::vector<std::vector<BackendOption>> options_storage_;
+  std::vector<Entry> entries_;
+};
+
+} // namespace runtime
+} // namespace executorch

extension/module/module.h

@@ -15,6 +15,7 @@
 #include <vector>
 
 #include <executorch/runtime/executor/program.h>
+#include <executorch/extension/module/dynamic_backend_options_map.h>
 
 namespace executorch {
 namespace extension {
@@ -483,6 +484,12 @@ class Module {
     return update("forward", backend_options);
   }
 
+  ET_EXPERIMENTAL ET_NODISCARD inline runtime::Error update(
+      const std::string& method_name,
+      const runtime::DynamicBackendOptionsMap& backend_options) {
+    return update(method_name, backend_options.entries());
+  }
+
   /**
    * Retrieves the EventTracer instance being used by the Module.
    * EventTracer is used for tracking and logging events during the execution

extension/module/targets.bzl

@@ -17,6 +17,7 @@ def define_common_targets():
             ],
             exported_headers = [
                 "module.h",
+                "dynamic_backend_options_map.h",
             ],
             visibility = [
                 "@EXECUTORCH_CLIENTS",

extension/module/test/module_test.cpp

@@ -508,3 +508,18 @@ TEST_F(ModuleTest, TestUpdateNonExistentMethod) {
   const auto update_result = module.update("nonexistent", map.entries());
   EXPECT_NE(update_result, Error::Ok);
 }
+
+TEST_F(ModuleTest, TestUpdateSugarSyntax) {
+  Module module(stub_model_path_);
+  int new_num_threads = 4;
+
+  // Clean sugar syntax
+  const auto update_result = module.update("forward", 
+      {
+        {"StubBackend", {{IntKey("NumberOfThreads"), new_num_threads}}
+      },
+  );
+  
+  EXPECT_EQ(update_result, Error::Ok);
+  ASSERT_EQ(StubBackend::singleton().num_threads(), new_num_threads);
+}