sweet: add end-to-end integration test

This change adds an integration test for Sweet that 1) obtains assets,
2) generates a subset of assets (that don't take an obscenely long
time), 3) runs all the benchmarks exactly once under short mode.

Currently this test takes about 6 minutes to execute. It also uses just
over 4 GiB of memory and about 6 GiB of disk space.

Change-Id: Ia70efd92f0bd70f218b405aff7eb5a9e8ee4c912
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/378276
Reviewed-by: Michael Pratt <mpratt@google.com>
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
5 files changed