Use TestPointerController in libinputservice_test

This test is currently affecting SF state. Even though the bug is in SF,
add a workaround here while the SF is getting fixed to unbreak our
presubmit.

In the future, we can consider adding a proper integration test for
checking PointerController behaviour with the real SF.

Bug: 301657737
Test: atest libinputservice_test
Test: atest VirtualDpadTest

Change-Id: Ia70e13add397ba10bde36a07d132e8dbc252eacd