Switch over to use use blocks from nostrdb

This is still kind of broken until queries are switched over to nostrdb.
Will do this next

Signed-off-by: William Casarin <jb55@jb55.com>

nostrdb/NdbBlocksIterator.swift

@@ -0,0 +1,59 @@
+//
+//  NdbBlockIterator.swift
+//  damus
+//
+//  Created by William Casarin on 2024-01-25.
+//
+
+import Foundation
+
+
+struct BlocksIterator: IteratorProtocol {
+    typealias Element = NdbBlock
+
+    var done: Bool
+    var iter: ndb_block_iterator
+    var note: NdbNote
+
+    mutating func next() -> NdbBlock? {
+        guard iter.blocks != nil,
+              let ptr = ndb_blocks_iterate_next(&iter) else {
+            done = true
+            return nil
+        }
+
+        let block_ptr = ndb_block_ptr(ptr: ptr)
+        return NdbBlock(block_ptr)
+    }
+
+    init(note: NdbNote, blocks: NdbBlocks) {
+        let content = ndb_note_content(note.note.ptr)
+        self.iter = ndb_block_iterator(content: content, blocks: nil, block: ndb_block(), p: nil)
+        ndb_blocks_iterate_start(content, blocks.as_ptr(), &self.iter)
+        self.done = false
+        self.note = note
+    }
+}
+
+struct BlocksSequence: Sequence {
+    let blocks: NdbBlocks
+    let note: NdbNote
+
+    init(note: NdbNote, blocks: NdbBlocks) {
+        self.blocks = blocks
+        self.note = note
+    }
+
+    func makeIterator() -> BlocksIterator {
+        return .init(note: note, blocks: blocks)
+    }
+    
+    func collect() -> [NdbBlock] {
+        var xs = [NdbBlock]()
+        for x in self {
+            xs.append(x)
+        }
+        return xs
+    }
+}
+