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/pool/pool_conn.go

@@ -0,0 +1,34 @@
+package pool
+
+import (
+	"context"
+
+	"github.com/go-faster/errors"
+	"go.uber.org/atomic"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tdsync"
+)
+
+// ErrConnDead means that connection is closed and can't be used anymore.
+var ErrConnDead = errors.New("connection dead")
+
+// Conn represents Telegram MTProto connection.
+type Conn interface {
+	Run(ctx context.Context) error
+	Invoke(ctx context.Context, input bin.Encoder, output bin.Decoder) error
+	Ping(ctx context.Context) error
+	Ready() <-chan struct{}
+}
+
+type poolConn struct {
+	Conn
+	id      int64 // immutable
+	dc      *DC   // immutable
+	deleted *atomic.Bool
+	dead    *tdsync.Ready
+}
+
+func (p *poolConn) Dead() <-chan struct{} {
+	return p.dead.Ready()
+}