Show Histories Side-by-Side: history items are not updated after dropping an item on a not current history

**Describe the bug**
Currently, when items are dragged and dropped between histories in the multiple view, the history items in the target history are not being updated in if it's not the current history. This is because the `watchHistory` only watches for changes in the current history, and does not update others when items are dropped into other histories.

**Galaxy Version and/or server at which you observed the bug**
Galaxy Version: `dev` branch
Commit: bc7d8710ba97f833e3933bf02ae3655b823f3536

**To Reproduce**
Steps to reproduce the behavior:
1. Go to Show Histories Side-by-Side
2. Click on `Select histories`
3. Choose at least two history
4. Drag an item and drop it on a history that is not the current history
5. See the item has been copied to the history but the list is not updated

**Expected behavior**
History panel showing the latest changes.

**Proposed Solutions**
1- One possible solution to this issue is to modify the `watchHistory` to watch for changes, including adding or deleting an item from history or the status update for a running item, in all histories that are selected in the multiple view and when the user is using it.
2- Another solution is to update [this line](https://github.com/galaxyproject/galaxy/blob/47966341c91590aedab41b4488adf56647b4a094/client/src/components/History/CurrentHistory/HistoryPanel.vue#L401) to use `loadHistoryItems` and fetch all items again from the server.