skipmerge feedback 2.0

[xmo-odoo]

• If skipmerge is toggled by hand on an already forward-ported source (S not FW1), the FWs are not updated to skipmerge. However report_conflict during forward-port is based on the "current batch", so it remains set (because the fw_policy of self is still the default) leading to the PRs being detached and not updating correctly.
• During subsequent updates of the PRs, pings are not suppressed, leading to the source author being subscribed to all of them even as they're trying to adjust their changes.
• On PR update, it generates a warning which is clearly incorrect, saying that a cascading conflict lead to not updating the followup (runbot_merge.forwardport.updates.conflict.parent), look at the context of its original addition and potentially remove it entirely.

Observed on the sequence from odoo/odoo#205190