ContentCapture: Don't ignore events with changed composing/selection span

Currently, if the view has a TEXT_CHANGED event in the buffer with the
same text, the new event is ignored, even if the Composing or Selection
span is changed.

Bug: 184311217
Test: manual - move cursor quickly and check flushed event
Test: atest android.contentcaptureservice.cts.LoginActivityTest
Change-Id: I4de28576b138225f4e64ed93bcb0b9dd3ed0095c