[bsp][stm32] add a new bsp for stm32h723-st-nucleo board

Author: hywing

.github/workflows/bsp_buildings.yml

@@ -188,6 +188,7 @@ jobs:
                 - "stm32/stm32g474-st-nucleo"
                 - "stm32/stm32h563-st-nucleo"
                 - "stm32/stm32h503-st-nucleo"
+                - "stm32/stm32h723-st-nucleo"
                 - "stm32/stm32h743-armfly-v7"
                 - "stm32/stm32h743-atk-apollo"
                 - "stm32/stm32h743-openmv-h7plus"