Implement Dot representation of a VerkleTrie

[thomas-quadratic]

Description

Currently, there is no humanly readable string representation implemented for VerkleTrie.
However, this could be helpful for debugging for example.
This issue proposes to implement a method toDot, a textual format for graphs used in visualisations and in go-verkle

Expected behavior:
We expect toDot to return the representation of the tree in Dot format.
Nodes should have location as attribute.
BranchNodes should have the commitment as attribute.
SuffixNodes should have stem, leftCommitment and rightCommitment as attributes.
LeafNodes should have suffix and value as attributes.

Location could also be used to uniquely name the nodes.