[FL-1991] Rewrite flash driver (#813)

* Toolbox: fix null pointer dereference in manchester decoder.
* FuriHal: use MPU to protect from null pointer dereference, replace flash driver with our own implementation.

lib/toolbox/manchester-decoder.c

@@ -20,10 +20,10 @@ bool manchester_advance(
             new_state = manchester_reset_state;
         } else {
             if(new_state == ManchesterStateMid0) {
-                *data = false;
+                if (data) *data = false;
                 result = true;
             } else if(new_state == ManchesterStateMid1) {
-                *data = true;
+                if (data) *data = true;
                 result = true;
             }
         }