[16.0][FIX] connector_search_engine: export and delete on multi bindings

[lmignon]

Fix error when calling the methods export_record or delete_record from the se.binding model when called on a recordset with items from different se.backend.

The export and delete methods involves the use of a Backend Adapter to communicate with the target search engine. We then need to process the bindings by backend to call the correct adapter and ensure at same time a batch process of the requested operation for all the records linked to the same backend.

[lmignon]

cc @sebastienbeau @sbejaoui

[lmignon]

/ocabot merge patch

[OCA-git-bot]

@lmignon The merge process could not start, because command `git merge --no-ff -m 'Merge PR #173 into 16.0

Signed-off-by lmignon' tmp-pr-173` failed with output:

Auto-merging connector_search_engine/static/description/index.html
CONFLICT (content): Merge conflict in connector_search_engine/static/description/index.html
Auto-merging connector_search_engine/__manifest__.py
Auto-merging connector_search_engine/README.rst
CONFLICT (content): Merge conflict in connector_search_engine/README.rst
Automatic merge failed; fix conflicts and then commit the result.

[lmignon]

/ocabot merge patch

[OCA-git-bot]

Hey, thanks for contributing! Proceeding to merge this for you. Prepared branch 16.0-ocabot-merge-pr-173-by-lmignon-bump-patch, awaiting test results.

[OCA-git-bot]

Congratulations, your PR was merged at d29f0079da1cffab6a42b7977c3731701e6fa22e. Thanks a lot for contributing to OCA. ❤️