Reduce API proto vtable overhead by splitting decode functionality (#9541)

esphome/components/api/proto.cpp

@@ -8,7 +8,7 @@ namespace api {
 
 static const char *const TAG = "api.proto";
 
-void ProtoMessage::decode(const uint8_t *buffer, size_t length) {
+void ProtoDecodableMessage::decode(const uint8_t *buffer, size_t length) {
   uint32_t i = 0;
   bool error = false;
   while (i < length) {