Finish inbound E2E device lists (#1243)

* Add tests for device list updates

* Add stale_device_lists table and use db before asking remote for device keys

* Fetch remote keys if all devices are requested

* Add display_name col to store remote device names

Few other tweaks to make `Server correctly handles incoming m.device_list_update`
pass.

* Fix sqlite otk bug

* Unbuffered channel to block /send causing sytest to not race anymore

* Linting and fix bug whereby we didn't send updated dl tokens to the client causing a tightloop on /sync sometimes

* No longer assert staleness as Update blocks on workers now

* Back out tweaks

* Bugfixes

syncapi/types/types.go

@@ -112,6 +112,9 @@ type StreamingToken struct {
 }
 
 func (t *StreamingToken) SetLog(name string, lp *LogPosition) {
+	if t.logs == nil {
+		t.logs = make(map[string]*LogPosition)
+	}
 	t.logs[name] = lp
 }
 
@@ -173,12 +176,14 @@ func (t *StreamingToken) WithUpdates(other StreamingToken) (ret StreamingToken)
 		}
 		ret.Positions[i] = other.Positions[i]
 	}
+	ret.logs = make(map[string]*LogPosition)
 	for name := range t.logs {
 		otherLog := other.Log(name)
 		if otherLog == nil {
 			continue
 		}
-		t.logs[name] = otherLog
+		copy := *otherLog
+		ret.logs[name] = &copy
 	}
 	return ret
 }