Bounce refreshView to the UI thread

An async refresh dispatches refreshXyz on a worker goroutine, which then calls
refreshView -> PostRefreshUpdate -> HandleRender. Today the final
self.c.Render() inside ListContextTrait.HandleRender is what triggers a UI flush
from the worker. We're going to remove that Render() call, so prepare by
wrapping refreshView's body in OnUIThread.

This moves the entire rendering of the view (and the ReApplyFilter/ReApplySearch
stuff) to the UI thread, not just the layout. I don't expect this to make a
difference in practice, and it is already one step towards my long-term goal of
moving all view rendering to the UI thread (see
https://github.com/jesseduffield/lazygit/issues/2974#issuecomment-1729154768).