Revert^2 "Refactor HealthTestingUtils to use WaitUtils"

This reverts commit d643463911c48b95bc23e5eee0299273f88354db.

Reason for revert: Original problem solved. Resubmitting.

+ Adding support for providers returning nullable values to WaitUtils.waitForNullableValueToSettle.

Bug: 263319575
Test: presubmit + local
Change-Id: Ia69f8b4fe0b550fe73659a008d605c1721fef624
4 files changed