libtimeinstate: skip tests on non-supporting devices

Devices that can't support BPF time in state tracking (e.g. upgrading
devices without kernel support for perf event selinux hooks) currently
fail libtimeinstate_test without this failure indicating a bug or
incorrect behavior. To make test failures meaningful, skip the tests
on such devices instead of failing.

isTrackingUidTimesSupported() is now exercised by the SetUp()
function, making the IsTrackingSupported test redundant, so remove
that test.

Test: run libtimeinstate_test on device without time_in_state.o and
confirm all tests are skipped
Change-Id: I11bc5cc6b2e32f56c40852846fddd6790d6643b3
Signed-off-by: Connor O'Brien <connoro@google.com>