Fix PackedIntVector IndexOutOfBoundsException

This JE occurs because the Editor receives an ACTION_MOVE event and calls performCursorDrag() when the number of lines in the textview is reduced and the cursor position exceeds the maximum number of lines in the textview

If the line where the cursor was last is larger than the number of lines in the textview, the actual number of lines in the textview is returned.

Bug: 281228811
Test: manually
1.Enter message app
2.Input more than two lines in edittext, drag the cursor on the
last line and delete the last text in that line
(cherry picked from https://partner-android-review.googlesource.com/q/commit:64a89f02765c0c22139000396ec425026b088a59)

Change-Id: Ife117e1a577223ff1bcd28ab202a6a9c1e391f72