cspec: Remove redundancy in build rules and theory files for c-kernel builds

Removes files that were duplicated in cspec/$L4V_ARCH directories to exist directly in
the cspec directory and contain $L4V_ARCH switches where needed. This allows for a single
Makefile for building the C kernel and the KernelInc_C theory, which is different between
architectures, to still exist per L4V_ARCH.

As the build location of the C kernel, and the resulting kernel_all.c_pp artifact, is
moved this change needs to be reflected in all the theory files that refer to it.