Adding startUser tests without removing user at the end

When we create a user, the default is that we ask to initialize it whenever we change from one user to another, without removing that user from Android.
These tests will serve to demonstrate the execution time in the common case of using the start user.

Results:
startUser_uninitializedUser Mean (ms): 2026.75
startUser_startOnceBefore Mean (ms): 924.75

startUser_startTwiceBefore Mean (ms): 438.0

startAndUnlockUser Mean (ms): 2032.75
startAndUnlockUser_startTwiceBefore Mean (ms): 1134.25

switchUser_stopped Mean (ms): 3095.75
switchUser_stopped_realistic Mean (ms): 2403.25

Bug: 266192048
Bug: 266555909
Test: atest UserLifecycleTests#startUser_uninitializedUser
Test: atest UserLifecycleTests#startUser_startOnceBefore
Test: atest UserLifecycleTests#startUser_startTwiceBefore
Test: atest UserLifecycleTests#startAndUnlockUser
Test: atest UserLifecycleTests#startAndUnlockUser_startTwiceBefore
Test: atest UserLifecycleTests#switchUser_stopped
Test: atest UserLifecycleTests#switchUser_stopped_realistic
Change-Id: I1157431eb7f13b21ba2fd230e1148cd5eb09724e