feat: added utility to format MerkleTree and MerklePath to hex

Example formatted MerkleTree:

```
880abe452320966617646e7740b014954300f19a28780a0889d62ff33f4b0534
  1ade1369091efa31201e9b60c9c28874d0ddce5362b335135a6bb4c917285983
  3e60a9c843b4bb19f7a0572102e6507195f5240767a396335fd21981b048b807
    0100000000000000000000000000000000000000000000000000000000000000
    0200000000000000000000000000000000000000000000000000000000000000
    0300000000000000000000000000000000000000000000000000000000000000
    0400000000000000000000000000000000000000000000000000000000000000
```

Example formatted MerklePath:

```
[0400000000000000000000000000000000000000000000000000000000000000, 1ade1369091efa31201e9b60c9c28874d0ddce5362b335135a6bb4c917285983]
```

src/lib.rs

@@ -7,18 +7,13 @@ extern crate alloc;
 mod bit;
 pub mod hash;
 pub mod merkle;
+pub mod utils;
 
 // RE-EXPORTS
 // ================================================================================================
 
 pub use winter_crypto::{RandomCoin, RandomCoinError};
 pub use winter_math::{fields::f64::BaseElement as Felt, FieldElement, StarkField};
-pub mod utils {
-    pub use winter_utils::{
-        collections, string, uninit_vector, ByteReader, ByteWriter, Deserializable,
-        DeserializationError, Serializable, SliceReader,
-    };
-}
 
 // TYPE ALIASES
 // ================================================================================================

src/merkle/merkle_tree.rs

@@ -1,6 +1,9 @@
 use super::{Felt, MerkleError, MerklePath, NodeIndex, Rpo256, RpoDigest, Vec, Word};
-use crate::{utils::uninit_vector, FieldElement};
-use core::slice;
+use crate::{
+    utils::{string::String, uninit_vector, word_to_hex},
+    FieldElement,
+};
+use core::{fmt, slice};
 use winter_math::log2;
 
 // MERKLE TREE
@@ -157,6 +160,52 @@ impl MerkleTree {
     }
 }
 
+/// Utility to vizualize a [MerkleTree] in text.
+pub fn tree_to_text(tree: &MerkleTree) -> Result<String, fmt::Error> {
+    let indent = "  ";
+    let mut s = String::new();
+    s.push_str(&word_to_hex(&tree.root())?);
+    s.push('\n');
+    for d in 1..=tree.depth() {
+        let entries = 2u64.pow(d.into());
+        for i in 0..entries {
+            let index = NodeIndex::new(d, i);
+
+            let node = tree
+                .get_node(index)
+                .expect("The index must always be valid");
+
+            for _ in 0..d {
+                s.push_str(indent);
+            }
+            s.push_str(&word_to_hex(&node)?);
+            s.push('\n');
+        }
+    }
+
+    Ok(s)
+}
+
+/// Utility to vizualize a [MerklePath] in text.
+pub fn path_to_text(path: &MerklePath) -> Result<String, fmt::Error> {
+    let mut s = String::new();
+    s.push('[');
+
+    for el in path.iter() {
+        s.push_str(&word_to_hex(el)?);
+        s.push_str(", ");
+    }
+
+    // remove the last ", "
+    if path.len() != 0 {
+        s.pop();
+        s.pop();
+    }
+    s.push(']');
+
+    Ok(s)
+}
+
 // TESTS
 // ================================================================================================
 

src/merkle/mod.rs

@@ -15,7 +15,7 @@ mod index;
 pub use index::NodeIndex;
 
 mod merkle_tree;
-pub use merkle_tree::MerkleTree;
+pub use merkle_tree::{path_to_text, tree_to_text, MerkleTree};
 
 mod path;
 pub use path::{MerklePath, RootPath, ValuePath};

src/utils.rs

@@ -0,0 +1,21 @@
+use super::Word;
+use crate::utils::string::String;
+use core::fmt::{self, Write};
+
+// RE-EXPORTS
+// ================================================================================================
+pub use winter_utils::{
+    collections, string, uninit_vector, ByteReader, ByteWriter, Deserializable,
+    DeserializationError, Serializable, SliceReader,
+};
+
+/// Converts a [Word] into hex.
+pub fn word_to_hex(w: &Word) -> Result<String, fmt::Error> {
+    let mut s = String::new();
+
+    for byte in w.iter().flat_map(|e| e.to_bytes()) {
+        write!(s, "{byte:02x}")?;
+    }
+
+    Ok(s)
+}