move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/crypto/fill_bytes_test.go

@@ -0,0 +1,30 @@
+package crypto
+
+import (
+	"crypto/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestFillBytes(t *testing.T) {
+	tests := []struct {
+		name    string
+		bitSize int
+		result  bool
+	}{
+		{"Smaller", 255, true},
+		{"Equal", 256, true},
+		{"Bigger", 512, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			a := require.New(t)
+			b, err := rand.Prime(rand.Reader, tt.bitSize)
+			a.NoError(err)
+
+			var to [256 / 8]byte
+			a.Equal(tt.result, FillBytes(b, to[:]))
+		})
+	}
+}