feat(drivers): implemented serial passthrough (#27605)

* feat: implemented serial passthrough

* fix: used make format

* fix: changed function order to match other drivers

* fix: moved passthrough from systemcmds to drivers

* fix: renamed BITBANG_TIMER to UART_BITBANG_TIMER

* fix: used make format

* feat: added PASSTHRU_EN guard to start of dshot&pwm_out

* fix: made changing ESC channels more stable

* fix: adjusted naming of guards

* fix: changed include guard of bitbang

* fix: removed unused variable SER_PASS_BAUD

* fix: adjusted comments

* fix: adjusted print_usage() to match other drivers

* fix: remove bitbang_write_byte from public API and some buffer guard

* fix: added Serialpassthrough&Bitbang to exclude list of allyesconfig.py

* fix: added missing flag to print_usage()

ROMFS/px4fmu_common/init.d/rcS

@@ -539,8 +539,13 @@ else
 	else
 		commander start
 
-		dshot start
-		pwm_out start
+		if param compare -s PASSTHRU_EN 0
+		then
+			dshot start
+			pwm_out start
+		else
+			param set PASSTHRU_EN 0
+		fi
 	fi
 
 	#