Bug 2029668 [RS] - Remove orphan attachments from db after a record is updated (backport #7294)

[mergify]

We got a user report that Firefox on iOS is taking a lot of space ( also confirmed this is happening on Android too ). We managed to narrow it down to the quicksuggest-amp.sql db in remote settings being 1GB+ in some cases. See Slack thread for more context.

This happens because whenever we update a record's attachment or tombstone a record we never clean up the orphan attachments. This should happen for all collections. I am assuming this manifested itself in quicksuggest-amp because we update it frequently.

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This is an automatic backport of pull request #7294 done by [Mergify](https://mergify.com).

[rvandermeulen]

/taskcluster ci full

[rvandermeulen]

Approved for A-S 150.0.1