Fix CTS tests on multi sensor devices (mostly)

All tests are improved but can still fail due to flakiness
in cleanup (main cause seems to be stale enrollments).

Bug: 186600837
Bug: 186371020
Bug: 187250205

Test: atest CtsBiometricsTestCases

Change-Id: Iae516b912999c5eaac626a4147ffcb7ddac7472a