AP_HAL: do not gate AP_CRASHDUMP_ENABLED on bootloader

Also rename from HAL_CRASHDUMP_ENABLE

Removes code based on define rather than creating empty functions.  Makes it clearer what's going on in the callers.

libraries/AP_HAL/AP_HAL_Boards.h

@@ -277,6 +277,10 @@
 #define HAL_WITH_MCU_MONITORING 0
 #endif
 
+#ifndef AP_CRASHDUMP_ENABLED
+#define AP_CRASHDUMP_ENABLED 0
+#endif
+
 #ifndef HAL_HNF_MAX_FILTERS
 // On an F7 The difference in CPU load between 1 notch and 24 notches is about 2%
 // The difference in CPU load between 1Khz backend and 2Khz backend is about 10%

libraries/AP_HAL/Util.h

@@ -196,8 +196,11 @@ public:
     // log info on stack usage
     virtual void log_stack_info(void) {}
 
+#if AP_CRASHDUMP_ENABLED
     virtual size_t last_crash_dump_size() const { return 0; }
     virtual void* last_crash_dump_ptr() const { return nullptr; }
+#endif
+
 protected:
     // we start soft_armed false, so that actuators don't send any
     // values until the vehicle code has fully started