Move the stm32c0 sources, headers and boards into arch/arm/src/stm32c0,
arch/arm/include/stm32c0 and boards/arm/stm32c0, then finalize the split:
source each split family directly in arch/arm/Kconfig and boards/Kconfig and
remove the now-empty combined arch/arm/src/stm32f0l0g0 and
boards/arm/stm32f0l0g0 trees.
BREAKING CHANGE: The combined STM32F0/L0/G0/C0 architecture and board
paths were split into stm32f0, stm32l0, stm32g0, and stm32c0 directories.
Out-of-tree boards, include paths, source paths, and defconfigs must move
from stm32f0l0g0 to the matching split family.
Signed-off-by: raiden00pl <raiden00@railab.me>