Normalize whitespace of each Apertium output line

When translateLines pushes multiple strings through Apertium in a single API
call, strip leading/trailing whitespace from each of the returned strings.

Apertium.js already ensured that no leading/trailing whitespace is passed to
Apertium. However, in some cases Apertium can add extraneous leading/trailing
whitespace where none existed before (e.g. translating 'It is' from en to es).

This ensures that substring detection code has correct data to work on.

Bug: T76124
Change-Id: I676ad2d80bc6eb99757c984a31ba1f17b2225575
Merge "Normalize whitespace of each Apertium output line"