Data structure request: AVLTreeMap

I was surprised to see a BinaryTreeMap and a RedBlackTreeMap but no AVLTreeMap (given the fact that there is an AVLTree implementation in the library).

For the sake of completion, I'd like to see an AVLTreeMap added.

Look at the existing AVLTree and RedBlackTreeMap implementations in the repository to understand the structure. The new AVLTreeMap should follow similar patterns for a key-value map. Start by examining the interfaces and base classes used by other tree maps. Implement the AVL balancing logic within the map structure, ensuring it passes any existing tests for tree maps.

Written by the indexing model from the issue text.