Move mem_tracing from macro setting to using the MbedOS Config Settings

docs/reference/api/platform/MemTrace.md

@@ -2,7 +2,17 @@
 
 Mbed OS provides a set of functions that you can use to study the runtime memory allocation pattern of your software: which sections of the code allocate and free memory and how much memory they need.
 
-You must define the `MBED_MEM_TRACING_ENABLED` macro to enable memory tracing.
+You must enable the `memory-tracing-enabled` setting in the Mbed OS platform configuration options to enable memory tracing. The recommended way to enable this setting is to add it to your `mbed_app.json`:
+
+```
+{
+    "target_overrides": {
+        "*": {
+            "platform.memory-tracing-enabled": true
+        }
+    }
+}
+```
 
 You can use the `mbed_mem_trace_set_callback` API to set the callback for memory tracing. The callback is invoked every time you call standard allocation functions, such as `malloc`, `realloc`, `calloc` and `free`.
 
@@ -16,6 +26,6 @@ For a step-by-step guide about how to use optimize memory using runtime memory t
 
 [![View code](https://www.mbed.com/embed/?url=https://os.mbed.com/teams/mbed_example/code/memory_tracing_example/)](https://os.mbed.com/teams/mbed_example/code/memory_tracing_example/file/168ab14e6694/main.cpp)
 
-### Related content 
+### Related content
 
 - [Runtime memory tracing tutorial](/docs/development/tutorials/optimizing.html#runtime-memory-tracing).

docs/tutorials/optimize/memory/runtime_mem_trace.md

@@ -4,11 +4,15 @@ Running out of memory is a common problem with resource constrained systems such
 
 #### Using the memory tracer
 
-The memory tracer is not enabled by default. To enable it, you need to define the **`MBED_MEM_TRACING_ENABLED`** macro. The recommended way to define this macro is to add it to the list of macros defined in your `mbed_app.json`:
+The memory tracer is not enabled by default. To enable it, you need to enable the **`memory-tracing-enabled`** setting in the Mbed OS platform configuration options. The recommended way to enable this setting is to add it to your `mbed_app.json`:
 
 ```
 {
-    "macros": ["MBED_MEM_TRACING_ENABLED"]
+    "target_overrides": {
+        "*": {
+            "platform.memory-tracing-enabled": true
+        }
+    }
 }
 ```