[lib] Trim newline characters from sidebar titles

Summary:
There was a bug in D693. For any text messages with a newline character, getMessageTitle would return the string with the newline at the end.

This meant that it was possible for threads to have titles that end with a newline character, which broke the sidebar's MessageListHeaderTitle.

We really should've caught this in the test plan... getFirstNonQuotedRawLine is supposed to just get the first line, not including any newline characters.

Test Plan: Create a new sidebar from a text message with multiple lines

Reviewers: atul, karol-bisztyga, palys-swm

Subscribers: KatPo, zrebcu411, Adrian, subnub

Differential Revision: https://phabricator.ashoat.com/D860