The header is foc-specific. It used to shadow the generic one provided
by the base repository, which contradicts with the kernel-agnostic
Genode API. Hence, it had to be moved to a foc-specific location.
This patch unifies the CPU session interface across all platforms. The
former differences are moved to respective "native-CPU" interfaces.
NOVA is not covered by the patch and still relies on a custom version of
the core-internal 'cpu_session_component.h'. However, this will soon be
removed once the ongoing rework of pause/single-step on NOVA is
completed.
Fixes#1922
