ART: Refactor GenSelect, refactor gen_common accordingly

This adds a GenSelect method meant for selection of constants. The
general-purpose GenInstanceof code is refactored to take advantage of
this. This cleans up code and squashes a branch-over on ARM64 to a

Also add a slow-path for type initialization in GenInstanceof.

Bug: 16241558

(cherry picked from commit 90969af6deb19b1dbe356d62fe68d8f5698d3d8f)

Change-Id: Ie4494858bb8c26d386cf2e628172b81bba911ae5
10 files changed