This was originally introduced to reuse large handlers, but now only
LdaContextSlot and LdaCurrentContextSlot remain (both roughly 2-300
bytes in size).

Since handler reuse complicates lazy (de)serialization and currently
doesn't seem to give us significant advantages, let's remove this.

Bug: v8:6624
Change-Id: I6f19952632e10bd67677a825bbcb46d580a9d5c8
Reviewed-on: https://chromium-review.googlesource.com/758642Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49254}