[IMP] im_chat: added functionality to close focused chatView and set foc...

...us to next chatView on Esc keypress and added close button on chatList

- Task: https://www.odoo.com/web#id=8752&view_type=form&model=project.task&action=333&active_id=131
- Pad: https://pad.odoo.com/p/r.xvGFnNn6ejnaaRoX