Change add{StyleRun, ReplacementRun} to append{StyleRun, ReplacementRun}

Giving any range to the Builder is too much freedum and hard to tell
errors. Changes to accept length instead of ranges. By this change, we
can prevent and tell errors about
- The gap in the text that no Paint is assigned.
- The given range is overlapped.
- The given range exceeds the text length.

Bug: 112327179
Test: TreeHugger

Change-Id: Iefc078b1f7be2d006a65b46e0b4ea1018ecb29e7