lib c/cpp: Move .ctor .init_array handling from C++ to kernel

* Move ctors and init_array from the CPP library
  to the kernel library, as this is common for both C
  and C++ and it is the kernel who is running it.
* Rename the hidden kconfig option CPP_STATIC_INIT_GNU
  STATIC_INIT_GNU instead.
* If STATIC_INIT_GNU is not selected verify there is
  constructors left behind.
* Rename common-rom-cpp.ld to common-rom-init.ld
* Rename z_cpp_init_static to z_init_static,
  and have the kernel always call it.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>
Signed-off-by: Keith Packard <keithp@keithp.com>