[native] Prevent multi-line thread titles in ThreadSettingsName

Summary:
For some reason this was configured (with extra work) to handle multi-line thread titles. Not sure what I was thinking.

This diff makes it impossible to set a thread title that continues newlines. Full context in D860 and D861.

Test Plan: Test ThreadSettingsName with multi-line thread titles

Reviewers: atul, karol-bisztyga, palys-swm

Subscribers: KatPo, zrebcu411, Adrian, subnub

Differential Revision: https://phabricator.ashoat.com/D862