De-optimize flicker tests

The library is used in tests only and doesn't need to be optimized. When optimization is enabled, the IDE breakpoints don't work correctly and some variables are not available, making it harder to debug.

Test: atest FlickerTests WMShellFlickerTests -w and put a breakpoint in any test
Bug: 162925924
Change-Id: I642cf86473573847d10b0ed452246e8742487684