refactor: Mmr accumulator

feat: add .inner_nodes() to [MerkleStore]

Tracking PR for v0.4 release

store: support adding existing structures

feat: allow merging of leaves

Consider the case of a MMR with one entry, and a new entry is being
added. Both of these values are quite unique, they are at the same time
the root and only leaf of their corresponding tree. Currently this
representation is not supported by the [MerkleStore], so the leaves are
not in it. Once the two values are merged, they both become leaves of a
new tree under the new parent, and the existing validation didn't permit
that promotion from happening.

This lifts the validation, and changes the method to clarify that not
only `root` are being merged, by arbitrary nodes of a tree (leafs,
internal, or roots), with arbitrary mixing of each.

re-export mmr proof

config: add rustfmt config

Tracking PR for v0.3 release

BLAKE3 hash_elements() optimization

feat: add `MerkleStore::get_leaf_depth`

This commit introduces `get_leaf_depth`, a tiered SMT helpers that will
retrieve the depth of a leaf for a given root, capped by `64`.

closes #119

mmr: optimized peak hash for Miden VM

Merkle fixes

feat: add parent node iterator for SimpleSMT

feat: add support for MMR to the MerkleStore

feat: add node iterator to MerkleTree

Remove SimpleSmt store

feat: Add `depth` as store SMT argument

Prior to this commit, MerkleStore allowed the creation of Sparse Merkle
tree only with the maximum depth of 63. However, this doesn't fit the
Tiered Sparse Merkle tree requirements, as it will contain trees of
depth 16.

This commit adds the `depth` argument to the MerkleStore methods that
will create Sparse Merkle trees.

v0.2 tracking PR

Prepare v0.2 release

bugfix: fix internal nodes of for empty leafs of a SMT

The path returned by `EmptySubtreeRoots` starts at the root, and goes to
the leaf. The MerkleStore constructor assumed the other direction, so
the parent/child hashes were reversed.

This fixes the bug and adds a test.

Add serde to merklestore