Add THERMAL_PROTECTION capability

Based on #10465

In response to `M115` the firmware reports if Thermal Protection is enabled (1) or not (0). This information can be used by software such as OctoPrint (more precisely the Printer Safety Check plugin) to warn users when Thermal Protection is not enabled in the firmware.

Co-Authored-By: andrivet <sebastien@advtools.com>

Marlin/src/gcode/host/M115.cpp

@@ -146,5 +146,12 @@ void GcodeSuite::M115() {
       #endif
     );
 
+    // THERMAL_PROTECTION
+    cap_line(PSTR("THERMAL_PROTECTION")
+      #if ENABLED(THERMAL_PROTECTION_HOTENDS) && ENABLED(THERMAL_PROTECTION_BED)
+        , true
+      #endif
+    );
+
   #endif // EXTENDED_CAPABILITIES_REPORT
 }