tests: In slower tests, make the timeout per-test-case

tests: In slower tests, make the timeout per-test-case

Some test-cases in the dbus-daemon and relay tests spam the bus with
thousands of messages, which can take 25 seconds on slower CPUs like
MIPS. Similarly, the refs test spams millions of refcount operations,
which it appears might take more than a minute on PA-RISC (HPPA).

To get an idea of how close we are to having a problem on other
architectures, log a message and start a timer when we reset the
timeout in setup(), and log the elapsed time when we reach teardown().

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=103009
Signed-off-by: Simon McVittie <smcv@collabora.com>
Reviewed-by: Philip Withnall <withnall@endlessm.com>