Improve test efficiency and stablility

* Run uninstallRebootlessApex (which reboots the device, thus slow) only
  necessarily in test cases.
* Use EasterEgg from the device, not a local build. Surprisingly this
  app is signed with the platform key, so a different build can have
  different key thus may fail to install.
* Increase waiting time to 30 seconds. For some reason that scheduling
  may not happen very soon, even on real device.
* Always cancel the pending job before starting a test. For example,
  this can cancel a job scheduled at boot, so that we can correctly
  verify that a package install actually triggers a job scheduling.
* Add a simply check to uniqueness of expected APEX list.

Bug: 265244016
Test: atest BinaryTransparencyServiceTest BinaryTransparencyHostTest

Change-Id: I4b7bf232be2ee74b6c0129bc9938c680f1835619