Develop a robust token contract update mechanism

[kantp]

Proposed feature

A go-to solution for updating a deployed fungible token contract to the newest version

Why

We expect the fungible token contract to evolve over time, as new features are implemented, performance is improved, etc. Even if there were no new features, the code would occasionally need to change just in order to keep up with upstream changes in o1js.

The current status is that the admin contract allows updating the main token contract. The default/example admin contract requires a signature from the deployer for an update of the token contract. This is not idea, as it establishes the deployer as a central authority who is needed for updating the contract, and who also has the power to do arbitrary changes.

We want to avoid this, and ensure that token contracts can be updated without relying on the deployer. We also want to ensure that when a contract is updated, it is updated to a legitimate newer version of the fungible token standard, as opposed to changed arbitrarily.