[lib] fix PushHandler to support DMs

Summary: Solution described in [ENG-9465](https://linear.app/comm/issue/ENG-9465/messages-from-thick-thread-notifs-dont-seem-to-be-integrated-into#comment-685bf427).

Test Plan:
Apply this diff:
1. Comment [this](https://github.com/CommE2E/comm/blob/cfc5daf4fbc477221cbd541241e6d9a6fc0774ca/lib/tunnelbroker/peer-to-peer-message-handler.js#L142) line to make sure we're testing actual notifs code & add some logs to make sure code in reducer was executed.
2. Open physical device
3. In DM thread send a test message
4. Notif delivered
5. Message immediately visible in UI
6. Thread marked as unread
5. Logs from reducer are there

Reviewers: ashoat, kamil

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D13576

lib/reducers/thread-reducer.js

@@ -335,8 +335,38 @@ function reduceThreadInfos(
     const changedThreadInfos: { [string]: RawThreadInfo } = {};
     for (const [threadID, mostRecentTime] of threadIDToMostRecentTime) {
       const threadInfo = state.threadInfos[threadID];
+      if (!threadInfo) {
+        continue;
+      }
+
+      if (threadInfo.thick) {
+        if (threadInfo.timestamps.currentUser.unread > mostRecentTime) {
+          continue;
+        }
+        changedThreadInfos[threadID] = {
+          ...threadInfo,
+          timestamps: {
+            ...threadInfo.timestamps,
+            currentUser: {
+              ...threadInfo.timestamps.currentUser,
+              unread: mostRecentTime,
+            },
+          },
+        };
+        if (!threadInfo.currentUser.unread) {
+          changedThreadInfos[threadID] = {
+            ...changedThreadInfos[threadID],
+            currentUser: {
+              ...threadInfo.currentUser,
+              unread: true,
+            },
+          };
+        }
+        continue;
+      }
+
       if (
-        !threadInfo ||
+        !action.payload.updatesCurrentAsOf ||
         threadInfo.currentUser.unread ||
         action.payload.updatesCurrentAsOf > mostRecentTime
       ) {

lib/types/message-types.js

@@ -669,7 +669,7 @@ export type GenericMessagesResult = {
 
 export type SaveMessagesPayload = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
-  +updatesCurrentAsOf: number,
+  +updatesCurrentAsOf: ?number,
 };
 
 export type NewMessagesPayload = {

native/push/push-handler.react.js

@@ -668,9 +668,6 @@ class PushHandler extends React.PureComponent<Props, State> {
     for (const keyserverID in keyserverIDToMessageInfos) {
       const updatesCurrentAsOf = this.props.allUpdatesCurrentAsOf[keyserverID];
       const messageInfos = keyserverIDToMessageInfos[keyserverID];
-      if (!updatesCurrentAsOf) {
-        continue;
-      }
 
       this.props.dispatch({
         type: saveMessagesActionType,