Draft: Add initial support for CH32H417 (#1023)

[So1aric]

This draft adds initial support for the CH32H417. Currently, I can generate a flashable binary in which the V3F core wakes up the V5F and toggles PC2, while the V5F toggles PC3.
However, I'm not quite satisfied with the build system yet. Since the firmware for the two cores must be compiled separately, the add_firmware call should somehow accept two source paths. For now, I've added addDualCoreFirmware in the port's build.zig as a workaround — I'm not sure whether this is the right approach, so feedback is welcome.
The HAL is still unfinished, and system_init remains to be implemented.
That said, I'd like to settle on the build system design first before moving on to the remaining implementation.

[So1aric]

#1023