internal/stats: add edm/edmx detectors

Add single-instance edm/edmx breakout detectors. These algorithms are
described in the paper:

https://courses.cit.cornell.edu/nj89/docs/edm.pdf

This implementation was compared against an open-source R
implementation, and yielded the same breakouts for a wide range of data
from cmd/bent.

Change-Id: I088e37e6444e3c9d3275a15d04b5cecf6e1d2fe9
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/292549
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>
5 files changed