[16.0][IMP] stock_available_to_promise_release: Unrelease when merging moves

[lmignon]

When moves are merged into an outgoing picking and the product_uom_qty is updated it's important to unrelease the move since the release process has been done for the previous qty. This case occurs for example when the qty is modified for a line on a confirmed SO.

[lmignon]

cc @rousseldenis @jbaudoux

[OCA-git-bot]

This PR has the approved label and has been created more than 5 days ago. It should therefore be ready to merge by a maintainer (or a PSC member if the concerned addon has no declared maintainer). 🤖

[rousseldenis]

@jbaudoux