Add support WeActStudio.STM32H7R3Zx CoreBoard

[acronis2000]

Please add a new board from WeAct Studio:

WeActStudio.STM32H7R3Zx_CoreBoard
STM32H7R3Z8J6 (600Mhz Max,620KB RAM,64KB ROM + 8MB Flash)

https://github.com/WeActStudio/WeActStudio.STM32H7R3Zx_CoreBoard/tree/master

[fpistm]

Hi @acronis2000

unfortunately, STM32H7R/S is not supported by the core.
See #2829.
I add this request to the new variant request list.