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/telegram/internal/manager/sync.go

@@ -0,0 +1,29 @@
+package manager
+
+import (
+	"sync/atomic"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+// AtomicConfig is atomic tg.Config.
+type AtomicConfig struct {
+	atomic.Value
+}
+
+// NewAtomicConfig creates new AtomicConfig.
+func NewAtomicConfig(cfg tg.Config) *AtomicConfig {
+	a := &AtomicConfig{}
+	a.Store(cfg)
+	return a
+}
+
+// Load loads atomically config and returns it.
+func (c *AtomicConfig) Load() tg.Config {
+	return c.Value.Load().(tg.Config)
+}
+
+// Store saves given config atomically.
+func (c *AtomicConfig) Store(cfg tg.Config) {
+	c.Value.Store(cfg)
+}