🔨 Creality v4 with STM32 HAL (#21999)

- New STM32 env for Creality V4 boards.
- Separate Libmaple targets into their own `ini` file.
- Temporarily remove unusable targets from `pins.h`.

Co-authored-by: ellensp <ellensp@hotmsil.com>
Co-authored-by: Scott Lahteine <github@thinkyhead.com>

buildroot/tests/STM32F103RC_btt_USB

@@ -10,7 +10,7 @@ set -e
 # Build with the default configurations
 #
 restore_configs
-opt_set MOTHERBOARD BOARD_BTT_SKR_MINI_V1_1 SERIAL_PORT 1 SERIAL_PORT_2 -1 BAUDRATE_2 115200
+opt_set MOTHERBOARD BOARD_BTT_SKR_MINI_V1_1 SERIAL_PORT 1 SERIAL_PORT_2 -1
 exec_test $1 $2 "BigTreeTech SKR Mini v1.1 - Basic Configuration" "$3"
 
 # clean up