Reduce usages of main looper in sysui tests

Push over to a standard testable looper, and a testable looper +
setAsMain when needed.

Also make tests more synchronous and single threaded as possible.
This will make them more deterministic and speeds them up noticeably.

Test: runtest systemui
Bug: 79550837
Change-Id: Iab0eb794329d7b1de95aef904ec08ecae7dadc98