benchmarks: move assets, and use embed to encode

Change-Id: I4a4003fafbbbec7cdf21b331749071050e92d229
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/290432
Trust: Jeremy Faller <jeremy@golang.org>
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
26 files changed