ndb: switch to nostrdb notes

This is a refactor of the codebase to use a more memory-efficient
representation of notes. It should also be much faster at decoding since
we're using a custom C json parser now.

Changelog-Changed: Improved memory usage and performance when processing events

damus/Util/DisplayName.swift

@@ -60,7 +60,6 @@ func parse_display_name(profile: Profile?, pubkey: Pubkey) -> DisplayName {
     return .one(abbrev_bech32_pubkey(pubkey: pubkey))
 }
 
-func abbrev_bech32_pubkey(pubkey: String) -> String {
-    let pk = bech32_nopre_pubkey(pubkey) ?? pubkey
-    return abbrev_pubkey(pk)
+func abbrev_bech32_pubkey(pubkey: Pubkey) -> String {
+    return abbrev_pubkey(String(pubkey.npub.dropFirst(4)))
 }