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/tgtest/buffered.go

@@ -0,0 +1,63 @@
+package tgtest
+
+import (
+	"context"
+	"sync"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/transport"
+)
+
+type bufferedConn struct {
+	conn transport.Conn
+
+	recv    []bin.Buffer
+	recvMux sync.Mutex
+}
+
+func newBufferedConn(conn transport.Conn) *bufferedConn {
+	return &bufferedConn{conn: conn}
+}
+
+func (c *bufferedConn) push(b *bin.Buffer) {
+	c.recvMux.Lock()
+	c.recv = append(c.recv, bin.Buffer{Buf: b.Copy()})
+	c.recvMux.Unlock()
+}
+
+func (c *bufferedConn) pop() (r bin.Buffer, ok bool) {
+	c.recvMux.Lock()
+	defer c.recvMux.Unlock()
+	if len(c.recv) < 1 {
+		return
+	}
+	r, c.recv = c.recv[len(c.recv)-1], c.recv[:len(c.recv)-1]
+	ok = true
+	return
+}
+
+func (c *bufferedConn) Push(b *bin.Buffer) {
+	c.push(b)
+}
+
+func (c *bufferedConn) Pop() (bin.Buffer, bool) {
+	return c.pop()
+}
+
+func (c *bufferedConn) Send(ctx context.Context, b *bin.Buffer) error {
+	return c.conn.Send(ctx, b)
+}
+
+func (c *bufferedConn) Recv(ctx context.Context, b *bin.Buffer) error {
+	e, ok := c.Pop()
+	if ok {
+		b.ResetTo(e.Copy())
+		return nil
+	}
+
+	return c.conn.Recv(ctx, b)
+}
+
+func (c *bufferedConn) Close() error {
+	return c.conn.Close()
+}