flag a bunch of method functions as deprecated (#523)

Summary:

None of these should exist in the public API, but we are out of time before MVP so just deprecating

Differential Revision: D49747135

Author: JacobSzwejbka

runtime/executor/method.cpp

@@ -1100,6 +1100,10 @@ Error Method::execute() {
   return experimental_reset_execution();
 }
 
+Result<MethodMeta> Method::method_meta() const {
+  return program_->method_meta(serialization_plan_->name()->c_str());
+}
+
 size_t Method::values_size() const {
   return n_value_;
 }

runtime/executor/method.h

@@ -12,6 +12,7 @@
 #include <executorch/runtime/core/event_tracer.h>
 #include <executorch/runtime/core/exec_aten/exec_aten.h>
 #include <executorch/runtime/executor/memory_manager.h>
+#include <executorch/runtime/executor/method_meta.h>
 #include <executorch/runtime/platform/compiler.h>
 
 // Forward declare flatbuffer types. This is a public header and must not
@@ -196,17 +197,32 @@ class Method final {
    */
   __ET_NODISCARD Error experimental_reset_execution();
 
-  size_t values_size() const;
-  const EValue& get_value(size_t i) const;
-  EValue& mutable_value(size_t i);
+  /**
+   * Gathers metadata for the named method.
+   *
+   * @returns the MethodMeta that corresponds to the calling Method.
+   */
+  Result<MethodMeta> method_meta() const;
+
+  __ET_DEPRECATED size_t values_size() const;
+  __ET_DEPRECATED const EValue& get_value(size_t i) const;
+  __ET_DEPRECATED EValue& mutable_value(size_t i);
   size_t inputs_size() const;
-  size_t get_input_index(size_t i) const;
-  const EValue& get_input(size_t i) const;
-  EValue& mutable_input(size_t i);
+  /// DEPRECATED: Use MethodMeta instead to access metadata, and set_input to
+  /// update Method inputs.
+  __ET_DEPRECATED size_t get_input_index(size_t i) const;
+  /// DEPRECATED: Use MethodMeta instead to access metadata, and set_input to
+  /// update Method inputs.
+  __ET_DEPRECATED const EValue& get_input(size_t i) const;
+  /// DEPRECATED: Use MethodMeta instead to access metadata, and set_input to
+  /// update Method inputs.
+  __ET_DEPRECATED EValue& mutable_input(size_t i);
   size_t outputs_size() const;
-  size_t get_output_index(size_t i) const;
+  __ET_DEPRECATED size_t get_output_index(size_t i) const;
   const EValue& get_output(size_t i) const;
-  EValue& mutable_output(size_t i);
+  /// DEPRECATED: Use MethodMeta instead to access metadata, and get_output to
+  /// retrieve Method outputs.
+  __ET_DEPRECATED EValue& mutable_output(size_t i);
   ~Method();
 
  private: