mcs: Rename CONFIG_KERNEL_RT to CONFIG_KERNEL_MCS

This is to be consistent with the name defined in the kernel.

Trivial: Style fix

make the style checker happy

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'

sel4utils: use provided fault ep, allow cptr

- allow a cptr in addition to a vka_object to be provided
to process_config when setting a fault endpoint
- actually set the flag that uses this field when creating a process

sel4utils: abstract over MCS vs master kernel API

- add api.h, which is intended to be used as a wrapper for functions
that are equivalent on MCS/master kernels, so we can seemlessly switch
between the two. This makes porting efforts easier, and without a
nasty proliferation of #ifdefs.
- use it everywhere relevant.

to squash: fail if non-RT kernel tries to create SC

Add scheduling context support in seL4_libs

Only works if CONFIG_KERNEL_RT is enabled, however most of the code
is compiled no mater what to lighten the maintenance burden

libsel4utils: Pass TCB cptr of new process in environment variable

If a cptr for the new processes TCB (in its cspace) is known, then this will pass
it as an environment variable to the newly created process. This provides a generic
way for a new process to invoke and modify its own TCB

sel4utils: consolidate config sched params

Threads and processes have the same scheduling parameters.
The MCS kernel expands on these, and this reduces duplication
between the two config structs.

libsel4utils: add const modifier

sel4utils: refactor process and thread config interface

- add builder patterns for thread and process configs which reduces api
breakage when new features are added
- replace all usages of configs with builders
- don't set priorities in default functions (threads will be set to 0)
- set MCP in threads and processes when specified