Reland "Allow a RingBuffer to take a value that is not copyable"

This is a reland of commit 99868713108025f007b88c9d3b5daa97428c5213

Patch set 1 is as landed. Fixes added are that ring_buffer.h
is actually added to a BUILD.gn, this caused CQ to accept the
file without actually really building anything substaintal. The
other is a fix to speedometer.cc to actually construct the object
explicitly.

Original change's description:
> Allow a RingBuffer to take a value that is not copyable
>
> Allow movable types in ring buffers.
>
> Change-Id: I8dae23b06d84065c0d151d83b0814f5cfb5460ca
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6613003
> Reviewed-by: Mark Mentovai <mark@chromium.org>
> Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1468288}

Change-Id: I5dc8010e3e3433acf75dc440ee9466fb8516057d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6611342
Reviewed-by: Mark Mentovai <mark@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1468387}