Apply #pragma once, misc cleanup (#12322)

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

Marlin/src/feature/solenoid.h

@@ -19,12 +19,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
-#ifndef __SOLENOID_H__
-#define __SOLENOID_H__
+#pragma once
 
 void enable_solenoid_on_active_extruder();
 void disable_all_solenoids();
 void enable_solenoid(const uint8_t num);
-
-#endif // __SOLENOID_H__