Test only: extend timeout to detect slow callbacks.

WallpaperManagerService observer perf regressed quite a lot. But this was not caught by benchmarks because there is 3s fixed overall timeout.
This change allows benchmarks to increase the timeout and observe the overall latency.

Test: atest UserLifecycleTests#switchUser --iterations
Bug: 165030092
Bug: 195145506
Change-Id: I335035da3aa0b76243fc2ad60022ecc4a08b0076