Apply #pragma once, misc cleanup (#12322)

* Apply #pragma once in headers
* Adjust some thermistors formatting
* Misc cleanup and formatting

Marlin/src/HAL/shared/backtrace/backtrace.h

@@ -19,11 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
-#ifndef _BACKTRACE_H_
-#define _BACKTRACE_H_
+#pragma once
 
 // Perform a backtrace to the serial port
 void backtrace(void);
-
-#endif