fix(all): introduce and use iox.CopyContext (#380)

* fix(all): introduce and use iox.CopyContext

This PR is part of https://github.com/ooni/probe/issues/1417.

In https://github.com/ooni/probe-cli/pull/379 we introduced a context
aware wrapper for io.ReadAll (formerly ioutil.ReadAll).

Here we introduce a context aware wrapper for io.Copy.

* fix(humanize): more significant digits

* fix: rename humanize files to follow the common pattern

* fix aligment

* fix test

internal/engine/experiment/ndt7/download.go

@@ -82,7 +82,7 @@ func (mgr downloadManager) doRun(ctx context.Context) error {
 			}
 			continue
 		}
-		n, err := io.Copy(io.Discard, reader)
+		n, err := iox.CopyContext(ctx, io.Discard, reader)
 		if err != nil {
 			return err
 		}

internal/engine/experiment/ndt7/ndt7.go

@@ -19,7 +19,7 @@ import (
 
 const (
 	testName    = "ndt"
-	testVersion = "0.8.0"
+	testVersion = "0.9.0"
 )
 
 // Config contains the experiment settings

internal/engine/experiment/ndt7/ndt7_test.go

@@ -17,7 +17,7 @@ func TestNewExperimentMeasurer(t *testing.T) {
 	if measurer.ExperimentName() != "ndt" {
 		t.Fatal("unexpected name")
 	}
-	if measurer.ExperimentVersion() != "0.8.0" {
+	if measurer.ExperimentVersion() != "0.9.0" {
 		t.Fatal("unexpected version")
 	}
 }

internal/engine/experiment/urlgetter/runner.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"io"
 	"io/ioutil"
 	"net/http"
 	"net/http/cookiejar"
@@ -13,6 +12,7 @@ import (
 	"github.com/ooni/probe-cli/v3/internal/engine/httpheader"
 	"github.com/ooni/probe-cli/v3/internal/engine/netx"
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/errorx"
+	"github.com/ooni/probe-cli/v3/internal/iox"
 	"github.com/ooni/probe-cli/v3/internal/runtimex"
 )
 
@@ -92,7 +92,7 @@ func (r Runner) httpGet(ctx context.Context, url string) error {
 		return err
 	}
 	defer resp.Body.Close()
-	if _, err = io.Copy(ioutil.Discard, resp.Body); err != nil {
+	if _, err = iox.CopyContext(ctx, ioutil.Discard, resp.Body); err != nil {
 		return err
 	}
 	// Implementation note: we shall check for this error once we have read the

internal/engine/netx/dialer/bytecounter_test.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/bytecounter"
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/mockablex"
+	"github.com/ooni/probe-cli/v3/internal/iox"
 )
 
 func dorequest(ctx context.Context, url string) error {
@@ -27,7 +28,7 @@ func dorequest(ctx context.Context, url string) error {
 	if err != nil {
 		return err
 	}
-	if _, err := io.Copy(ioutil.Discard, resp.Body); err != nil {
+	if _, err := iox.CopyContext(ctx, ioutil.Discard, resp.Body); err != nil {
 		return err
 	}
 	return resp.Body.Close()

internal/engine/session_integration_test.go

@@ -3,7 +3,6 @@ package engine
 import (
 	"context"
 	"errors"
-	"io"
 	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
@@ -17,6 +16,7 @@ import (
 	"github.com/ooni/probe-cli/v3/internal/engine/geolocate"
 	"github.com/ooni/probe-cli/v3/internal/engine/model"
 	"github.com/ooni/probe-cli/v3/internal/engine/probeservices"
+	"github.com/ooni/probe-cli/v3/internal/iox"
 	"github.com/ooni/probe-cli/v3/internal/version"
 )
 
@@ -31,7 +31,8 @@ func TestSessionByteCounter(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer resp.Body.Close()
-	if _, err := io.Copy(ioutil.Discard, resp.Body); err != nil {
+	ctx := context.Background()
+	if _, err := iox.CopyContext(ctx, ioutil.Discard, resp.Body); err != nil {
 		t.Fatal(err)
 	}
 	if s.KibiBytesSent() <= 0 || s.KibiBytesReceived() <= 0 {