Override RoleManager for KeyGestureEventTests

It's possible that the device may not have defaults or certain roles
supported. To still allow these tests to run properly, the role manager
should be overridden.

Bug: 364802899
Test: atest com.android.server.policy.KeyGestureEventTests
Flag: TEST_ONLY
Change-Id: I803d590ec5bbf0fb85c32957fbd259693c3463b8