Slightly more precise RTL check in BoringLayout.isBoring()

This patch refines the crude check for potential RTL characters, based
on ranges containing RTL scripts and format characters that affect
bidi. This will make it much less likely that a StaticLayout will be
chosen instead of a BoringLayout.

Bug: 22328919
Change-Id: I9a0ed9b3f3373069052de21c836b3372f175430f