Fix launcher activity leak in TouchInteractionService

TouchInteractionService cannot be garbage collected until it has been cleared from the sysui process. Switching to use a WeakReference to help with garbage collection.

Flag: not needed
Bug: 283490010
Test: ran launcher and performed gestures
Change-Id: I37aa5f858f2ae0ac78b46478ab4c5f24770bd64f
4 files changed