feat(core): delete related notifications when deleting identifier

[iFergal]

Description

We generally cannot act on notifications that relate to deleted identifiers, and we shouldn't anyway. #969 skips any incoming notifications related to deleted identifiers, and handles long running operations that complete which are related to deleted identifiers.

This PR will delete all notification records that are related to an identifier being deleted (and the local group member too, if applicable). This way the user cannot get into an error state acting on old notifications. Also included is a small cleanup in general.

Finally, I also decided we should sync deleted identifiers locally. We soft delete identifiers for historical reasons, so they should be re-synced because other areas of the code assumes the identifier metadata record might exist. We can refactor in the future to fully delete instead of soft deleting and handle the idempotency.

For example, if you delete a group and the local group member identifier has been marked as deleted on the cloud, but fails from there on/crashes, and then you recover on a new device, if you try to delete the group again it will fail as it assumes there's a local group member identifier record in the local DB. This fixes that edge case.

Checklist before requesting a review

Issue ticket number and link

• This PR has a valid ticket number or issue: [link]

Testing & Validation

• This PR has been tested/validated in IOS, Android and browser.
• The code has been tested locally with test coverage match expectations.
• Added new Unit/Component testing (if relevant).