feat: use go1.16 and resources embedding (#235)

* feat: use go1.16 embedding for resources

We want to embed everything that can be easily embedded. We should, at a
minimum, replace the downloading of resources and bindata.

Ref: https://github.com/ooni/probe/issues/1367.

* fix: get rid of bindata and use go embed instead

* fix: start unbreaking some automatic tests

* fix: fetch resources as part of the mobile build

* fix: convert more stuff to go1.16

I still expect many breakages, but we'll fix them.

* fix: make the windows CI green

* fix: get resources before running QA

* fix: go1.16 uses modules by default

* hopefully fix all other outstanding issues

* fix(QA/telegram.py): add another DC IP address

* Apply suggestions from code review

internal/engine/resourcesmanager/resourcesmanager_test.go

@@ -0,0 +1,142 @@
+package resourcesmanager
+
+import (
+	"errors"
+	"io"
+	"io/fs"
+	"os"
+	"testing"
+)
+
+func TestAllGood(t *testing.T) {
+	// make sure we start from scratch
+	if err := os.RemoveAll("testdata"); err != nil {
+		t.Fatal(err)
+	}
+	// first iteration should copy the resources
+	cw := &CopyWorker{DestDir: "testdata"}
+	if err := cw.Ensure(); err != nil {
+		t.Fatal(err)
+	}
+	// second iteration should just ensure they're there
+	if err := cw.Ensure(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestEmptyDestDir(t *testing.T) {
+	cw := &CopyWorker{DestDir: ""}
+	if err := cw.Ensure(); !errors.Is(err, ErrDestDirEmpty) {
+		t.Fatal("not the error we expected", err)
+	}
+}
+
+func TestMkdirAllFailure(t *testing.T) {
+	errMocked := errors.New("mocked error")
+	cw := &CopyWorker{
+		DestDir: "testdata",
+		MkdirAll: func(path string, perm os.FileMode) error {
+			return errMocked
+		},
+	}
+	if err := cw.Ensure(); !errors.Is(err, errMocked) {
+		t.Fatal("not the error we expected", err)
+	}
+}
+
+func TestOpenFailure(t *testing.T) {
+	errMocked := errors.New("mocked error")
+	cw := &CopyWorker{
+		DestDir: "testdata",
+		MkdirAll: func(path string, perm os.FileMode) error {
+			return nil
+		},
+		ReadFile: func(path string) ([]byte, error) {
+			return []byte(`fake`), nil
+		},
+		Equal: func(left, right string) bool {
+			return false
+		},
+		Open: func(path string) (fs.File, error) {
+			return nil, errMocked
+		},
+	}
+	if err := cw.Ensure(); !errors.Is(err, errMocked) {
+		t.Fatal("not the error we expected", err)
+	}
+}
+
+func TestNewReaderFailure(t *testing.T) {
+	errMocked := errors.New("mocked error")
+	cw := &CopyWorker{
+		DestDir: "testdata",
+		MkdirAll: func(path string, perm os.FileMode) error {
+			return nil
+		},
+		Equal: func(left, right string) bool {
+			return false
+		},
+		NewReader: func(r io.Reader) (io.ReadCloser, error) {
+			return nil, errMocked
+		},
+	}
+	if err := cw.Ensure(); !errors.Is(err, errMocked) {
+		t.Fatal("not the error we expected", err)
+	}
+}
+
+func TestReadAllFailure(t *testing.T) {
+	errMocked := errors.New("mocked error")
+	cw := &CopyWorker{
+		DestDir: "testdata",
+		MkdirAll: func(path string, perm os.FileMode) error {
+			return nil
+		},
+		Equal: func(left, right string) bool {
+			return false
+		},
+		ReadAll: func(r io.Reader) ([]byte, error) {
+			return nil, errMocked
+		},
+	}
+	if err := cw.Ensure(); !errors.Is(err, errMocked) {
+		t.Fatal("not the error we expected", err)
+	}
+}
+
+func TestSHA256Mismatch(t *testing.T) {
+	cw := &CopyWorker{
+		DestDir: "testdata",
+		MkdirAll: func(path string, perm os.FileMode) error {
+			return nil
+		},
+		Equal: func(left, right string) bool {
+			return false
+		},
+		Different: func(left, right string) bool {
+			return true
+		},
+	}
+	if err := cw.Ensure(); !errors.Is(err, ErrSHA256Mismatch) {
+		t.Fatal("not the error we expected", err)
+	}
+}
+
+func TestWriteFileFailure(t *testing.T) {
+	errMocked := errors.New("mocked error")
+	cw := &CopyWorker{
+		DestDir: "testdata",
+		MkdirAll: func(path string, perm os.FileMode) error {
+			return nil
+		},
+		Equal: func(left, right string) bool {
+			return false
+		},
+		WriteFile: func(filename string, data []byte, perm fs.FileMode) error {
+			return errMocked
+		},
+	}
+	if err := cw.Ensure(); !errors.Is(err, errMocked) {
+		t.Fatal("not the error we expected", err)
+	}
+}