Update Rust to 1.84.1 (#5508)

- also update the crates
- add necessary modifications for `rand` upgrade
- `small_rng` is enabled by default now

src/crypto.rs

@@ -56,11 +56,11 @@ pub fn encode_random_bytes<const N: usize>(e: Encoding) -> String {
 pub fn get_random_string(alphabet: &[u8], num_chars: usize) -> String {
     // Ref: https://rust-lang-nursery.github.io/rust-cookbook/algorithms/randomness.html
     use rand::Rng;
-    let mut rng = rand::thread_rng();
+    let mut rng = rand::rng();
 
     (0..num_chars)
         .map(|_| {
-            let i = rng.gen_range(0..alphabet.len());
+            let i = rng.random_range(0..alphabet.len());
             alphabet[i] as char
         })
         .collect()