Chat in new tab

[MarcMcIntosh]

#40

TODO
[x] render chats in a a new tab
[x] refactor chatTab to handle both the side bar and a tab
[x] improve the ui when the tab gets large.
[x] discuss options for keeping data in sync.
[ ] handle other user flows, (from tab back to side bar chat and possibly others)
[x] disable buttons when waiting for responses

[ ] add padding to the top of the chat tab
[ ] new file should work
[ ] stop should work

User flows

[ ] Click on chat in history -> expand chat in sidebar
[ ] Click on a button on chat in history -> expand chat in tab
[x] Chat in sidebar -> option to move to tab
[ ] Chat in tab -> option to move to sidebar

note:
In order to go from tab to sidebar we'll need to figure out how to programatically close the webview panel. so far I've tried window.close, and tab.dispose with no luck :/

TBD:
Should we add serialisation so the windows persist when the editor is reloaded?
https://code.visualstudio.com/api/extension-guides/webview#serialization