refactor: miniooni should be outside of the engine (#206)

* refactor: miniooni should be outside of the engine

This is part of https://github.com/ooni/probe/issues/1335. We also need
to think whether we wanna keep libminiooni and miniooni separated.

The previous use case for having a top-level libminiooni was that of
enabling others to integrate miniooni into other binaries.

This was usegul when studying internet censorship in Spain in May 2020.

I am wondering whether we should be keeping this complexity. I am not
sure about this and probably we should be killing it.

(In any case, reducing complexity is not the objective of this diff,
since I would like instead to move things around with minimal changes
and make sure we have a ~good repository organization here.)

* fix: import in libminiooni

internal/engine/internal/humanizex/humanizex.go

@@ -1,26 +0,0 @@
-// Package humanizex is like dustin/go-humanize
-package humanizex
-
-import "fmt"
-
-// SI is like dustin/go-humanize.SI
-func SI(value float64, unit string) string {
-	value, prefix := reduce(value)
-	return fmt.Sprintf("%3.0f %s%s", value, prefix, unit)
-}
-
-func reduce(value float64) (float64, string) {
-	if value < 1e03 {
-		return value, " "
-	}
-	value /= 1e03
-	if value < 1e03 {
-		return value, "k"
-	}
-	value /= 1e03
-	if value < 1e03 {
-		return value, "M"
-	}
-	value /= 1e03
-	return value, "G"
-}