Add test legacy trace stub

Bug: 181199209
Test: gd/cert/run
Tag: #refactor
BYPASS_LONG_LINES_REASON: Bluetooth likes 120 lines

Change-Id: Ie5be989255c5609da81b6126c266f18f45007e83

system/test/stub/legacy_trace.cc

+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <cstdint>
+
+// tLEGACY_TRACE_LEVEL
+uint8_t btu_trace_level = 6;
+uint8_t appl_trace_level = 6;
+uint8_t btif_trace_level = 6;
+
+uint8_t A2DP_SetTraceLevel(uint8_t new_level) { return 0; }
+uint8_t AVDT_SetTraceLevel(uint8_t new_level) { return 0; }
+uint8_t AVRC_SetTraceLevel(uint8_t new_level) { return 0; }
+uint8_t BNEP_SetTraceLevel(uint8_t new_level) { return 0; }
+uint8_t BTM_SetTraceLevel(uint8_t new_level) { return 0; }
+uint8_t PAN_SetTraceLevel(uint8_t new_level) { return 0; }
+uint8_t PORT_SetTraceLevel(uint8_t new_level) { return 0; }
+uint8_t SMP_SetTraceLevel(uint8_t new_level) { return 0; }