a11y: Add first-time use dialog for key gestures (2/n)

This patch provides
* Implemented the interactor
* Implement the unittest and the kosmos or it

Bug: b/410892855
Flag: com.android.hardware.input.enable_talkback_and_magnifier_key_gestures
Test: atest KeyGestureDialogInteractorTest
Change-Id: I7d692b7df4c33d956962b5a16e452f84b7fd0b7e