Parallelize 'channel_sign' calls.

## Issue
If the account has lots of channels, each channel name was sequentially signed, delaying the final action.

ui/redux/actions/comments.js

@@ -489,6 +489,22 @@ export function doCommentUpdate(comment_id: string, comment: string) {
   }
 }
 
+async function channelSignName(channelClaimId: string, channelName: string) {
+  let signedObject;
+
+  try {
+    signedObject = await Lbry.channel_sign({
+      channel_id: channelClaimId,
+      hexdata: toHex(channelName),
+    });
+
+    signedObject['claim_id'] = channelClaimId;
+    signedObject['name'] = channelName;
+  } catch (e) {}
+
+  return signedObject;
+}
+
 // Hides a users comments from all creator's claims and prevent them from commenting in the future
 export function doCommentModToggleBlock(channelUri: string, unblock: boolean = false) {
   return async (dispatch: Dispatch, getState: GetState) => {
@@ -512,18 +528,6 @@ export function doCommentModToggleBlock(channelUri: string, unblock: boolean = f
     const creatorNameForAction = claim ? claim.name : null;
 
     let channelSignatures = [];
-    if (myChannels) {
-      for (const channelClaim of myChannels) {
-        try {
-          const channelSignature = await Lbry.channel_sign({
-            channel_id: channelClaim.claim_id,
-            hexdata: toHex(channelClaim.name),
-          });
-
-          channelSignatures.push({ ...channelSignature, claim_id: channelClaim.claim_id, name: channelClaim.name });
-        } catch (e) {}
-      }
-    }
 
     const sharedModBlockParams = unblock
       ? {
@@ -536,9 +540,15 @@ export function doCommentModToggleBlock(channelUri: string, unblock: boolean = f
         };
 
     const commentAction = unblock ? Comments.moderation_unblock : Comments.moderation_block;
+
+    return Promise.all(myChannels.map((channel) => channelSignName(channel.claim_id, channel.name)))
+      .then((response) => {
+        channelSignatures = response;
         // $FlowFixMe
         return Promise.allSettled(
-      channelSignatures.map((signatureData) =>
+          channelSignatures
+            .filter((x) => x !== undefined && x !== null)
+            .map((signatureData) =>
               commentAction({
                 mod_channel_id: signatureData.claim_id,
                 mod_channel_name: signatureData.name,
@@ -563,6 +573,12 @@ export function doCommentModToggleBlock(channelUri: string, unblock: boolean = f
               type: unblock ? ACTIONS.COMMENT_MODERATION_UN_BLOCK_FAILED : ACTIONS.COMMENT_MODERATION_BLOCK_FAILED,
             });
           });
+      })
+      .catch(() => {
+        dispatch({
+          type: unblock ? ACTIONS.COMMENT_MODERATION_UN_BLOCK_FAILED : ACTIONS.COMMENT_MODERATION_BLOCK_FAILED,
+        });
+      });
   };
 }
 
@@ -588,21 +604,15 @@ export function doFetchModBlockedList() {
     });
 
     let channelSignatures = [];
-    if (myChannels) {
-      for (const channelClaim of myChannels) {
-        try {
-          const channelSignature = await Lbry.channel_sign({
-            channel_id: channelClaim.claim_id,
-            hexdata: toHex(channelClaim.name),
-          });
 
-          channelSignatures.push({ ...channelSignature, claim_id: channelClaim.claim_id, name: channelClaim.name });
+    return Promise.all(myChannels.map((channel) => channelSignName(channel.claim_id, channel.name)))
-        } catch (e) {}
+      .then((response) => {
-      }
+        channelSignatures = response;
-    }
         // $FlowFixMe
         return Promise.allSettled(
-      channelSignatures.map((signatureData) =>
+          channelSignatures
+            .filter((x) => x !== undefined && x !== null)
+            .map((signatureData) =>
               Comments.moderation_block_list({
                 mod_channel_id: signatureData.claim_id,
                 mod_channel_name: signatureData.name,
@@ -653,6 +663,12 @@ export function doFetchModBlockedList() {
               type: ACTIONS.COMMENT_MODERATION_BLOCK_LIST_FAILED,
             });
           });
+      })
+      .catch(() => {
+        dispatch({
+          type: ACTIONS.COMMENT_MODERATION_BLOCK_LIST_FAILED,
+        });
+      });
   };
 }