refactor: optimize historical note retrieval

[juan518munoz]

Notable changes:

• Removes the manual Client::fetch_all_private_notes and replaces it with an automatic per tag backfill, so consumers no longer have to fetch history themselves after they start tracking a new tag.
• The automatic backfill runs on every sync. Notes related to a newly tracked tag are fetched the first time it becomes tracked (after add_note_tag, an account import, or an address creation).
• The client keeps track of already covered tags, by storing them in the settings table under note_transport_covered_tags.

Note:

This branch cherry-picks the NTL 0.4.1 upgrade from #2264, as PR landed on main and next does not have it yet, so its three commits are replayed here because the backfill depends on 0.4.1 (the block_hint delivery path).

Closes #2258

[SantiagoPittella]

this can be joined

[juan518munoz]

Addressed in ab58f42