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/Models/Reply.swift

@@ -12,21 +12,20 @@ struct ReplyDesc {
     let others: Int
 }
 
-func make_reply_description(_ tags: [[String]]) -> ReplyDesc {
+func make_reply_description(_ tags: Tags) -> ReplyDesc {
     var c = 0
     var ns: [Pubkey] = []
-    var i = tags.count - 1
-        
-    while i >= 0 {
-        let tag = tags[i]
-        if tag.count >= 2 && tag[0] == "p" {
+    var i = tags.count
+
+    for tag in tags {
+        if let pk = Pubkey.from_tag(tag: tag) {
             c += 1
             if ns.count < 2 {
-                ns.append(tag[1])
+                ns.append(pk)
             }
         }
         i -= 1
     }
-        
+
     return ReplyDesc(pubkeys: ns, others: c)
 }