CMake: Move direct configurations out of settings

KernelDomainSchedule, ApplyData61ElfLoaderSettings, LibNanopb are
configurations that don't take a user configuration for seL4test.
Instead we move them closer to where they are directly used.

Move UserLinkerGCSections out of main settings

Now that sel4test controls when build flags get enumerated, this option
can be moved closer to the configuration step it affects.

CMake: Refactor CMake project to import modules

Instead of sel4test being a project that gets imported into the seL4
build system, sel4test can import the seL4 dependencies into its own
project via CMake modules. This is to make the build structure easier to
understand and build upon as projects will no longer get added
automatically by existing inside the ./projects directory.

CMake: Set config options to advanced if forced

If Sel4testAllowSettingsOverride isn't set, Sel4testHaveTimer,
Sel4testHaveCache and LibSel4TestPrintXML cannot be set so we mark them
as advanced. This then gets reset when Sel4testAllowSettingsOverride is
set.

sel4test: explicitly link sel4_autoconf

since the global conf lib is going be removed, we need to explicitly
linke each project with sel4_autoconf and other config libs
this commit also removed a bunch of unused includes as well as
HAVE_AUTOCONF ifdef checking.

sel4test: remove autoconf.h from sel4test

this commit removes autoconf.h generation from sel4test and
append '#include <sel4test/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'

trivial: style changed files

sel4test-tests: request serial caps from driver

Since we can only allocate individual frame capabilities once, currently
sel4test passes the serial frame into test processes explicitly.

We remove this explicit mechanism, and make sel4test-tests send a RPC
message to the test driver to request these frames when they're
allocated.

Depend on sel4runtime.

SELFOUR-1056/sel4test: Add backend support for timer server and wait for tests

SELFOUR-1056/sel4test: move timer interrupt tests for sel4test-test to sel4test-driver

* Add time-related helper files.
* Move code in sel4test/tests/interrupts to sel4test-driver/src/tests/timer.c
* Add a new function to do sel4test-driver tests before sel4test-test tests

SELFOUR-1083 extract test cases from sel4test-tests using elf magic instead of bash script

Add README to describe how to declare tests

Add CMake configuration files

Add CMake build rules for building the two sel4test applications