doFetchModBlockedList: don't block ui thread

doFetchModBlockedList is blocking the ui thread.

Duplicate data in `doFetchModBlockedList::blockListsPerChannel` to about 1000. The tab is dead when function hits, about 4s after reload.

- Yield occasionally using the `setTimeout` method.
- Doing a chunk size of 1 for now so we don't have to yield the inner loop as well (seems good enough). This is just based on a relatively large blocklist size.

- Can't do `await` in a callback, so must change the `forEach` to a `for`.

ui/redux/actions/comments.js

@@ -1143,6 +1143,9 @@ export function doCommentModUnBlockAsModerator(commenterUri: string, creatorUri:
 
 export function doFetchModBlockedList() {
   return async (dispatch: Dispatch, getState: GetState) => {
+    const LOOP_CHUNK_SIZE = 1;
+    const yieldThread = () => new Promise((resolve) => setTimeout(resolve));
+
     const state = getState();
     const myChannels = selectMyChannelClaims(state);
     if (!myChannels) {
@@ -1172,7 +1175,7 @@ export function doFetchModBlockedList() {
               })
             )
         )
-          .then((res) => {
+          .then(async (res) => {
             let personalBlockList = [];
             let adminBlockList = [];
             let moderatorBlockList = [];
@@ -1186,11 +1189,9 @@ export function doFetchModBlockedList() {
             const moderatorTimeoutMap = {};
 
             const blockListsPerChannel = res.map((r) => r.value);
-            blockListsPerChannel
-              .sort((a, b) => {
-                return 1;
-              })
-              .forEach((channelBlockLists) => {
+            blockListsPerChannel.sort((a, b) => 1);
+
+            for (let i = 0; i < blockListsPerChannel.length; ++i) {
               const storeList = (fetchedList, blockedList, timeoutMap, blockedByMap) => {
                 if (fetchedList) {
                   fetchedList.forEach((blockedChannel) => {
@@ -1231,10 +1232,15 @@ export function doFetchModBlockedList() {
                 }
               };
 
+              const channelBlockLists = blockListsPerChannel[i];
               const blocked_channels = channelBlockLists && channelBlockLists.blocked_channels;
               const globally_blocked_channels = channelBlockLists && channelBlockLists.globally_blocked_channels;
               const delegated_blocked_channels = channelBlockLists && channelBlockLists.delegated_blocked_channels;
 
+              if (i > 0 && i % LOOP_CHUNK_SIZE === 0) {
+                await yieldThread();
+              }
+
               storeList(blocked_channels, personalBlockList, personalTimeoutMap);
               storeList(globally_blocked_channels, adminBlockList, adminTimeoutMap);
               storeList(
@@ -1243,7 +1249,7 @@ export function doFetchModBlockedList() {
                 moderatorTimeoutMap,
                 moderatorBlockListDelegatorsMap
               );
-              });
+            }
 
             dispatch({
               type: ACTIONS.COMMENT_MODERATION_BLOCK_LIST_COMPLETED,