refactor: make measurex depend on measurexlite (#892)

This diff makes `measurex` depend on `measurexlite` rather than the other way around.

While there, add unit tests.

Closes https://github.com/ooni/probe/issues/2240

internal/measurexlite/failure_test.go

@@ -0,0 +1,82 @@
+package measurexlite
+
+import (
+	"errors"
+	"io"
+	"testing"
+
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
+)
+
+func TestNewFailure(t *testing.T) {
+	type args struct {
+		err error
+	}
+	tests := []struct {
+		name string
+		args args
+		want *string
+	}{{
+		name: "when error is nil",
+		args: args{
+			err: nil,
+		},
+		want: nil,
+	}, {
+		name: "when error is wrapped and failure meaningful",
+		args: args{
+			err: &netxlite.ErrWrapper{
+				Failure: netxlite.FailureConnectionRefused,
+			},
+		},
+		want: func() *string {
+			s := netxlite.FailureConnectionRefused
+			return &s
+		}(),
+	}, {
+		name: "when error is wrapped and failure is not meaningful",
+		args: args{
+			err: &netxlite.ErrWrapper{},
+		},
+		want: func() *string {
+			s := "unknown_failure: errWrapper.Failure is empty"
+			return &s
+		}(),
+	}, {
+		name: "when error is not wrapped but wrappable",
+		args: args{err: io.EOF},
+		want: func() *string {
+			s := "eof_error"
+			return &s
+		}(),
+	}, {
+		name: "when the error is not wrapped and not wrappable",
+		args: args{
+			err: errors.New("use of closed socket 127.0.0.1:8080->10.0.0.1:22"),
+		},
+		want: func() *string {
+			s := "unknown_failure: use of closed socket [scrubbed]->[scrubbed]"
+			return &s
+		}(),
+	}}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := NewFailure(tt.args.err)
+			if tt.want == nil && got == nil {
+				return
+			}
+			if tt.want == nil && got != nil {
+				t.Errorf("NewFailure:  want %+v, got %s", tt.want, *got)
+				return
+			}
+			if tt.want != nil && got == nil {
+				t.Errorf("NewFailure:  want %s, got %+v", *tt.want, got)
+				return
+			}
+			if *tt.want != *got {
+				t.Errorf("NewFailure:  want %s, got %s", *tt.want, *got)
+				return
+			}
+		})
+	}
+}