FIX: use the correct API of mail.channel.py to unfollow a channel
i.e.: `execute_command_leave`
FIX: unpinning a channel has immediate effect on the interface
chatWindows are closed, and the inbox is displayed
FIX: unpinning a channel destroys corresponding chatWindows across tabs
It also unpins the channel in other tabs
FIX: python sends is_pinned as part of the channel_info
both at init messaging and in the main bus notification
That way, we can keep track of the synchronization of the pin status
between JS and python
task-2275000
task-2267941
closesodoo/odoo#53703
X-original-commit: d4fcc64acb2fc0c6fd9df505380f665abd8b39c4
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>