We were registering `deploy` only on editors, which did succeed for
channel notes; however, channel note does not have an associated
workspace (that we pulled from the editor). It made more sense to just
register these actions for a workspace, notwithstanding the editor.

This PR also fixes a bunch of cx.dispatch_action calls to call the
handler directly instead (e.g. instead of dispatching ReplaceNext we
just call buffer_search_bar.replace_next instead) as otherwise these
actions are not handled if the buffer search bar does not have the
focus.

Release Notes:

- N/A