Track down usages of lines and convert to linesIterator

[farmdawgnation]

The issue scala/bug#11125 means that we need to track down usages of StringOps.lines and replace it with linesIterator in order to be safe.

We discovered this in #1953 while working on the JDK 11 and 12 builds.

[farmdawgnation]

I did a full search of the codebase for .lines across all *.scala files and only find one other area where we seem to invoke a function called lines. That is on the CompleteMenu object which defines its parts as a variable named lines. Specs might have been the only place we've leaned on StringOps.lines.

@Shadowfiend you wanna double check me before I close this out?

[Shadowfiend]

I'm 👍 here.