HoverService should support secondary windows

[sdirix]

Bug Description:

When prompting a hover tooltip, it is shown in the original window instead of the secondary window

Steps to Reproduce:

1. Extract Chat View to secondary window
2. Send any message.
3. Hover over the agent
4. The tooltip shows in the original window, instead of the secondary window

Expected behavior:
The tooltip shows in the secondary window

It's likely the hover service which needs an overhaul to properly support secondary windows. It's used here in the described scenario. This seems to be the culprit code.

Additional Information

• Operating System: Ubuntu 22.04
• Theia Version: Latest master 73ff47b

[tsmaeder]

There are more uses of document in that file that we should review.