Add explicit check to not trigger a cursor drag via the mouse

Cursor drag without the handle is only for touch and should not trigger
for events from a mouse. This was already the case before this CL but it
was not explicit: SelectionModifierCursorController happened to trigger
first so the cursor drag would not get activated. This change updates
the cursor drag logic so that mouse events are explicitly excluded from
the feature.

Bug: 145535274
Bug: 143852764
Test: Manual and automated tests
  atest FrameworksCoreTests:EditorCursorDragTest
  atest FrameworksCoreTests:TextViewActivityMouseTest

Change-Id: I3ccf5106b8e9a9e3c271dff38a4d6a0c0aa19597