[Adapter Module]: Implement Metastable Token Adapter

[njokuScript]

Description

Create a token adapter contract that facilitates the burning and minting of metastable tokens. The adapter should interact directly with the Vault Contracts to manage metastable balances.

Tasks

• Design the metastable token adapter contract interface
• Implement functions for minting and burning of metastable tokens as well as representing the balance on the vault contracts
• Integrate the adapter with the Vault Contracts
• Write tests to ensure the functionality of the metastable token adapter

NB: This was previously implemented here: https://github.com/Descent-Collective/protocol-core/blob/module/adapter/contracts/adapter.sol#L89