replace kernel_autoconf with sel4_autoconf

since the mainline kernel's kernel_autoconf doesn't include
seL4/gen_config.h but sel4_autoconf does

Trivial: Style fix

make the style checker happy

link kernel_autoconf explicitly

explicitly link kernel_autoconf on each subdirectory

seL4_libs: remove autoconf.h from seL4_libs

this commit removes autoconf.h generation from each lib and
append '#include <<lib_name>/gen_config.h>' after each
'#include <autoconf.h>' since autoconf.h is only the for the
kernel config now. This is a temporarily solution, since we
currently don't have a way to tell which header files each file
is trying to include when it includes 'autoconf.h'

Depend on sel4runtime for platsupport and utils

Platsupport and utils now need sel4runtime.

CMake: Mark config options as advanced

This is to hide the options in the cmake-gui. Top level applications can
choose to reexpose these options by clearing the advanced setting.

trivial: style CMakeLists.txt files

SELFOUR-1239: riscv: merge arch and sel4_arch/arch.c

- riscv doesn't need sel4_arch, remove it
- merge arch.c
- add src/arch to build files

Add time_server sources to cmake

Add CMake build rules for various libraries