Prevent crash for Span change events

For some spans, SpannableStringBuilder cannot determine the previous
start and previous end values correctly. In some cases, previous end
value is smaller than previous start value, and this causes
DynamicLayout to access negative index values. This CL updates
DynamicLayout to reflow from index 0 if such a case occurs.

Test: Added a CTS test
Test: bit CtsTextTestCases:android.text.cts.DynamicLayoutTest#testReflow_afterSpanChangedShouldNotThrowException

Bug: 67926915
Change-Id: Ibc55edfd5e49a7782cdd807e2465f4f21577b68d