cmd/bent: pull Configuration into its own file

Nonfunctional change, pulling the Configuration structure and methods
out of bent.go into a separate file.

Change-Id: Ic1db482eb7affe79d0dc596135a67fcea2eb1606
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/290731
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Jeremy Faller <jeremy@golang.org>
Run-TryBot: Jeremy Faller <jeremy@golang.org>
Reviewed-by: David Chase <drchase@google.com>
2 files changed