Example formatted MerkleTree:

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

Example formatted MerklePath:

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

Returning tuples is often confusing as they don't convey meaning and it
should be used only when there is no possible ambiguity.

For `MerkleStore`, we had a couple of tuples being returned, and reading
the implementation was required in order to distinguish if they were
leaf values or computed roots.

This commit introduces two containers that will self-document these
returns: `RootPath` and `ValuePath`. It will also update `set_node` to
return both the new root & the new path, so we can prevent duplicated
traversals downstream when updating a node (one to update, the second to
fetch the new path/root).

The store builds the path from root to leaf, this updates the code to
return a path from leaf to root, as it is done by the other structures.

This also added custom error for missing root.

Prior to this commit, the MerkleStore panicked under certain bounds. It
will prevent such panics by using checked operations.

ilog2, for instance, will panic when the operand is zero. However, there
is a documentation rule enforcing the merkle tree to be size at least 2.
If this rule is checked, then the panic is impossible.

Prior to this commit, there was an internal procedure with the merkle
trees to compute empty sub-tree for arbitrary depths.

However, this isn't ideal as this code can be reused in any merkle
implementation that uses RPO as backend.

This commit introduces a structure that will generate these empty
subtrees values.

This commit introduces a wrapper structure to encapsulate the merkle
tree traversal.

related issue: #36

A Merkle path is a vector of nodes, regardless of the Merkle tree
implementation.

This commit introduces an encapsulation for such vector, also to provide
functionality that is common between different algorithms such as
opening verification.

related issue: #36

This commit moves the previous implementation of `SparseMerkleTree` from
miden-core to this crate.

It also include a couple of new tests, a bench suite, and a couple of
minor fixes. The original API was preserved to maintain compatibility
with `AdviceTape`.

closes #21

closes #5