Improve/fix D23 for M2.5/S printers

- Move D23 into it's own function inside Dcodes
- Correctly include a break in the switch statement
- Show the dumper status (enabled/disabled) after toggling
- Allow to generate an immediate dump via g-code using D23 E for
  symmetry with D20 E

Firmware/Dcodes.cpp

@@ -974,6 +974,18 @@ void dcode_22()
 
 bool emergency_serial_dump = false;
 
+void dcode_23()
+{
+    if(code_seen('E'))
+        serial_dump_and_reset(dump_crash_reason::manual);
+    else
+    {
+        emergency_serial_dump = !code_seen('R');
+        SERIAL_ECHOPGM("serial dump ");
+        SERIAL_ECHOLNRPGM(emergency_serial_dump? _N("enabled"): _N("disabled"));
+    }
+}
+
 void __attribute__((noinline)) serial_dump_and_reset(dump_crash_reason reason)
 {
     uint16_t sp;