Re-enable chat in sidebar by default

Remaining TODO:

Re-enable chat in the sidebar and make this the default New Chat mode:

Non-functional changes:

Change VS Code command names to be more correct/consistent:

cody.chat.panel.new -> cody.chat.newEditorPanel
cody.chat.panel.sidebar.new -> cody.chat.newPanel
cody.chat.panel.moveFromSidebarToEditor -> cody.chat.moveToEditor
cody.chat.panel.moveFromEditorToSidebar -> cody.chat.moveFromEditor
Remove cody.chat.focus as an explicitly defined command, since we want a different title depending on whether the user is auth'd or unauth'd. Replace this with cody.chat.signIn and cody.chat.focusView, both of which just invoke cody.chat.focus, which is an implicitly defined command that focuses the cody.chat view

Avoid using "sidebar", because the chat view can be dragged to the bottom panel.

[ ] Pull down this branch
[ ] Execute the Cody: New Chat command from the command palette
[ ] Observe it creates the new chat in the sidebar. The sidebar should open if it's not yet open
[ ] Move the chat from the sidebar into an editor panel using the icon button in the panel header
[ ] Move the chat back into the sidebar from the editor using the icon button in the editor panel header
[ ] Execute the Cody: New Chat in Editor command and verify this still opens a new chat view in an editor panel