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/testutil/payloads.go

@@ -0,0 +1,26 @@
+package testutil
+
+import (
+	"fmt"
+	"testing"
+)
+
+// Payloads returns a payload sizes list.
+// Helpful for benchmarks.
+func Payloads() []int {
+	return []int{
+		16,
+		128,
+		1024,
+		8192,
+		64 * 1024,
+		512 * 1024,
+	}
+}
+
+// RunPayloads runs given benchmark runner for every payload.
+func RunPayloads(b *testing.B, runner func(size int) func(b *testing.B)) {
+	for _, size := range Payloads() {
+		b.Run(fmt.Sprintf("%db", size), runner(size))
+	}
+}