Return 0 in a test callback

The function is declared to return an int and clang will complain
if there is no return statement.

tests,timer: Use time manager instead of ltimer

For some platforms with small timer counter widths, there may be more
than one source of timer interrupts. This could lead to timestamp
overflow events being mistaken for the timeout events. So instead of
going directly to the ltimer to setup timeouts, we use the time manager
to manage the timeouts so that these both events are correctly managed.

sel4test-driver: Update timer interaction logic

Following from the move to the ltimer interface, this commit updates the
tests and support functions to interact with the timer properly.

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.

Trivial: style fix

make the style checker happy

sel4test: s/test_ge/test_gt and s/test_le/test_lt

SELFOUR-1146: Add test to check that ltimer moves between gettime calls

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