etcd: add benchmark

This change adds a benchmark that spins up a local cluster of 3 etcd
instances and runs etcd's benchmark tool against it.

For golang/go#59672.

Change-Id: I1c23439bad7bb16e055e689ddd4df8bf8d4b5288
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/492776
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
8 files changed