A serialization error can happen when chatting with another
user from the company. To reproduce:

- Log into Odoo as User A
- Open another Odoo tab in the same window as User A
- In private mode log into Odoo as User B
- Send a message via chat from User B to User A.

A concurrent update happens in channel_fetched method when writing
on mail_channel_partner.fetched_message_id.

To fix that, update the field
through raw SQL using FOR NO KEY UPDATE SKIP LOCKED in select subquery.
This skips the row should it be already locked, which is fine
as we only need to first transaction in the queue to complete.

opw-3164584

closes odoo/odoo#128154

X-original-commit: 757bfb69
Signed-off-by: Matthieu Stockbauer (tsm) <tsm@odoo.com>
Signed-off-by: Aurélien van Delft (avd) <avd@odoo.com>