This makes all data structures containing non-trivially-copyable fields
move-only, to prevent security and performance bugs.

Drive-by: Fix smaller performance bugs found by this refactoring.

R=titzer@chromium.org

Change-Id: I6802ac3591534c2ab5cacb2ca42b737f3b7fa801
Reviewed-on: https://chromium-review.googlesource.com/576170Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46747}