Associate slow paths with the instruction that they belong to.

Almost all slow paths already know the instruction they belong to,
this CL just moves the knowledge to the base class as well.

This is needed to be be able to get the corresponding dex pc for
slow path, which allows us generate better native line numbers,
which in turn fixes some native debugging stepping issues.

Change-Id: I568dbe78a7cea6a43a4a71a014b3ad135782c270