Respect feature flag when providing Pip controller

Makes sysui dagger provides optional PIP controller with PIP feature
flag. Adds test in PipControllerTest to make sure it won't instantiate
controller if the feature is not supported.

Bug: 170188471
Test: atest SystemUITests
Test: atest WMShellUnitTests
Change-Id: I681bb5ac2972d6426c270099605d44fc82dc9f78