Update on "[5.1/ N] set_option/get_option API with {backend_name, backend options} only"

This PR only expose the set_option/get_option API via the pair {backend_name, backend_options}, without necessarily backend options map. The backend options map and it's corresponding API will be exposed to another PR

Reference PR in #11758 which exposes the set_option/get_option with backendoptions map too

Differential Revision: [D77190316](https://our.internmc.facebook.com/intern/diff/D77190316/)

[ghstack-poisoned]

Author: cccclai

runtime/backend/interface.h

@@ -111,7 +111,7 @@ class BackendInterface {
    * @retval Error::Ok if successful.
    */
   ET_NODISCARD virtual Error set_option(
-      BackendOptionContext& context,
+      __ET_UNUSED BackendOptionContext& context,
       const executorch::runtime::Span<BackendOption>& backend_options) {
     return Error::Ok;
   };
@@ -127,7 +127,7 @@ class BackendInterface {
    * @retval Error::Ok if successful.
    */
   ET_NODISCARD virtual Error get_option(
-      BackendOptionContext& context,
+      __ET_UNUSED BackendOptionContext& context,
       executorch::runtime::Span<BackendOption>& backend_options) {
     return Error::Ok;
   };

runtime/backend/options.h

@@ -29,7 +29,7 @@ using OptionValue =
 struct BackendOption {
   // key is the name of the backend option, like num_threads, enable_profiling,
   // etc
-  char key[kMaxOptionKeyLength];
+  char key[kMaxOptionKeyLength]{};
   // value is the value of the backend option, like 4, true, etc
   OptionValue value;
 };
@@ -129,7 +129,7 @@ class BackendOptions {
   Error set_option(const char (&key)[N], const char* value) noexcept {
     static_assert(N <= kMaxOptionKeyLength, "Option key is too long");
     // Create a fixed-size array and copy the string
-    std::array<char, kMaxOptionValueLength> arr;
+    std::array<char, kMaxOptionValueLength> arr{};
     strncpy(arr.data(), value, kMaxOptionValueLength - 1);
     arr[kMaxOptionValueLength - 1] = '\0'; // Ensure null termination
     return set_option_impl(key, arr);

runtime/backend/test/backend_interface_update_test.cpp

@@ -40,23 +40,23 @@ class MockBackend : public BackendInterface {
   }
 
   Result<DelegateHandle*> init(
-      BackendInitContext& context,
-      FreeableBuffer* processed,
-      ArrayRef<CompileSpec> compile_specs) const override {
+      __ET_UNUSED BackendInitContext& context,
+      __ET_UNUSED FreeableBuffer* processed,
+      __ET_UNUSED ArrayRef<CompileSpec> compile_specs) const override {
     init_called = true;
     return nullptr;
   }
 
   Error execute(
-      BackendExecutionContext& context,
-      DelegateHandle* handle,
-      EValue** args) const override {
+      __ET_UNUSED BackendExecutionContext& context,
+      __ET_UNUSED DelegateHandle* handle,
+      __ET_UNUSED EValue** args) const override {
     execute_count++;
     return Error::Ok;
   }
 
   Error set_option(
-      BackendOptionContext& context,
+      __ET_UNUSED BackendOptionContext& context,
       const executorch::runtime::Span<BackendOption>& backend_options)
       override {
     set_option_count++;