New detector for getCurrentUser and getUserInfo

Detect slow calls to ActivityManager.getCurrentUser() or
UserManager.getUserInfo() and suggest using UserTracker instead.
For more info, see: http://go/multi-user-in-systemui-slides.

Test: manual
Bug: 238923086
Change-Id: I04a79ab3836a35a687d31af9e566a28d89aaeae6