Use uiautomator_helpers to open/close screen and wait for it to settle

Note:
I'm unsure about the actual root cause of the flakiness. Sometimes the
test stuck in screen off state.
Using the helper class provided by uiautomator_helpers seemed to make
the test more stable.

Bug: 337259815
Test: atest AccessibilityMenuServiceTest --iterations 50
Flag: NA
Change-Id: I95b1538bcc5f5f6fa6b6fd832b55afa00df8556a