Address STM32 cppcheck warnings (#11314)

- Suppress GenericThreadModule warning when DEBUG_MUTE
- Suppress warning stemming from check_skip_packages
- Cast pointers to uint32_t before subtracting to avoid cppcheck warning

src/memGet.cpp

@@ -23,7 +23,10 @@ static uint32_t sbrkHeadroom()
     extern char _estack;
     extern char _Min_Stack_Size;
 
-    uint32_t max_sp = (uint32_t)(&_estack - &_Min_Stack_Size);
+    // Both are linker-script symbols rather than real objects: _estack is the top-of-RAM address and
+    // _Min_Stack_Size is a plain value. Convert each to an integer before subtracting - differencing the
+    // pointers themselves is pointer arithmetic across unrelated objects.
+    uint32_t max_sp = (uint32_t)&_estack - (uint32_t)&_Min_Stack_Size;
     uint32_t heap_end = (uint32_t)sbrk(0);
     return (max_sp > heap_end) ? (max_sp - heap_end) : 0;
 }