feat: example to generate vanity node_ids (#3654)

Description
---
An example in tari_comms that generates vanity node_id's with a specified prefix. Used to generate node_ids for seed nodes.

comms/examples/vanity_id.rs

@@ -0,0 +1,61 @@
+// Copyright 2021. The Tari Project
+//
+// Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
+// following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following
+// disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
+// following disclaimer in the documentation and/or other materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote
+// products derived from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+// USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+use tari_comms::peer_manager::NodeId;
+use tari_crypto::{keys::PublicKey, ristretto::RistrettoPublicKey, tari_utilities::hex::Hex};
+
+#[tokio::main]
+async fn main() {
+    let mut rng = rand::thread_rng();
+
+    let mut target_hex_prefixes = vec!["3333", "5555", "7777", "9999", "bbbb", "dddd", "eeee"];
+    for i in 0u64..1_000_000_000u64 {
+        let (k, pk) = RistrettoPublicKey::random_keypair(&mut rng);
+        let node_id = NodeId::from_public_key(&pk);
+        let node_id_hex = node_id.to_hex();
+        if i % 10_000 == 0 {
+            println!("{}", i);
+        }
+
+        let mut found = "not found";
+        for p in target_hex_prefixes.iter() {
+            if &&node_id_hex.as_str()[0..p.len()] == p {
+                println!("Found in {} iterations", i);
+                println!("Secret Key: {}", k.to_hex());
+                println!("Public Key: {}", pk);
+                println!("Node Id: {}", node_id_hex);
+                println!("==================================================");
+                found = p;
+                break;
+            }
+        }
+
+        if found != "not found" {
+            let pos = target_hex_prefixes.iter().position(|p| *p == found).unwrap();
+            target_hex_prefixes.remove(pos);
+        }
+
+        if target_hex_prefixes.is_empty() {
+            break;
+        }
+    }
+}