fix compilation warning "infinite recursion detected"

In ESP-IDFv5.1 branch, more warnings are turned into error.
In particular here, `-Werror=infinite-recursion` gives the following error:
```
main/test_framework.cpp: In function 'void test_stackoverflow(int, OvmsWriter*, OvmsCommand*, int, const char* const*)':
main/test_framework.cpp:174:6: error: infinite recursion detected [-Werror=infinite-recursion]
  174 | void test_stackoverflow(int verbosity, OvmsWriter* writer, OvmsCommand* cmd, int argc, const char* const* argv)
      |      ^~~~~~~~~~~~~~~~~~
main/test_framework.cpp:180:21: note: recursive call
  180 |   test_stackoverflow(verbosity+1, writer, cmd, argc, argv);
      |   ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

We add an attribute to confirm that we know what we're doing here.

Signed-off-by: Ludovic LANGE <[email protected]>

vehicle/OVMS.V3/main/test_framework.cpp

@@ -171,6 +171,7 @@ void test_watchdog(int verbosity, OvmsWriter* writer, OvmsCommand* cmd, int argc
   writer->puts("Error: We should never get here");
   }
 
+__attribute__((noreturn))
 void test_stackoverflow(int verbosity, OvmsWriter* writer, OvmsCommand* cmd, int argc, const char* const* argv)
   {
   uint8_t data[256];