Avoid redundant strlen for shorty names

As the shorty names are ASCII, we can safely use the UTF16 length as
the byte length. Update several ART files to use the shorty getters
that return the length to avoid redundant strlen calls.

This strlen usage was showing up as a minor part of a recent Play Store
app startup profile.

Bug: 204230974
Test: Manual
Change-Id: I4f5fb100303f465ed50b524ee5e349c8341a05e9
3 files changed