nip19: Custom checksum with usize::MAX limit for bech32 decoding

[TheAwiteb]

Related: #723

Description

This patch introduces a custom checksum with a usize::MAX limit instead of the
previous limit of 1023.

Before this patch, the following code would not work. Now it works as expected:

use nostr::prelude::*;

const NPROFILE: &str = "...";

fn main() {
    let nprofile = Nip19Profile::from_bech32(NPROFILE).unwrap();
    println!("{}", nprofile.public_key);
    for (idx, relay) in nprofile.relays.iter().enumerate() {
        println!("{idx}: {relay}");
    }
}

Output:

Public Key: 813fce4c4e76f1e7b4f4697bf1030a90f1a0b783f187d329800a4dd8697f9759
0: wss://brb.io/
1: wss://brb.io/
2: wss://eden.nostr.land/
3: wss://eden.nostr.land/
4: wss://nos.lol/
5: wss://nos.lol/
6: wss://nostr-pub.wellorder.net/
7: wss://nostr-pub.wellorder.net/
8: wss://nostr.bitcoiner.social/
9: wss://nostr.fmt.wiz.biz/
10: wss://nostr.fmt.wiz.biz/
11: wss://nostr.relayer.se/
12: wss://nostr.relayer.se/
13: wss://nostr.wine/
14: wss://nostr.x0f.org/
15: wss://offchain.pub/
16: wss://offchain.pub/
17: wss://relay.current.fyi/
18: wss://relay.current.fyi/
19: wss://relay.damus.io/
20: wss://relay.damus.io/
21: wss://relay.mostr.pub/
22: wss://relay.nostr.band/
23: wss://relay.nostr.info/
24: wss://relay.nostr.info/
25: wss://relay.noswhere.com/
26: wss://relay.primal.net/
27: wss://relay.snort.social/
28: wss://relay.snort.social/

Notes to the reviewers

Why not encoding? I tried, but it produce a different nprofile, so I implemented decoding only.

Checklist

• I followed the contribution guidelines
• I ran just precommit or just check before committing
• I updated the CHANGELOG (if applicable)