decoder/Client: add Submit methods

Replaces decoder_data() and others.

src/decoder/plugins/AdPlugDecoderPlugin.cxx

@@ -73,9 +73,9 @@ adplug_file_decode(DecoderClient &client, Path path_fs)
 		int16_t buffer[2048];
 		constexpr unsigned frames_per_buffer = ARRAY_SIZE(buffer) / 2;
 		opl.update(buffer, frames_per_buffer);
-		cmd = decoder_data(client, nullptr,
-				   buffer, sizeof(buffer),
-				   0);
+		cmd = client.SubmitData(nullptr,
+					buffer, sizeof(buffer),
+					0);
 	} while (cmd == DecoderCommand::NONE);
 
 	delete player;