Treat touchpad taps as mouse taps

This is similar to
https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:recyclerview/recyclerview-selection/src/main/java/androidx/recyclerview/selection/MotionEvents.java;l=34-40;drc=f0fab6de9e079afce5bc7a1d9213f26b4ceb43c1

Bug: 389814214
Test: atest DocumentsUIGoogleTests:com.android.documentsui.dirlist.DragStartListenerTest
Flag: EXEMPT bugfix
Change-Id: Ia693e6e52e4c2213659f6f8ead607658db1f9dd5