Allow reuse of token contract, deploy contrib factory as upgradable proxy

[Doy-lee]

• The stagenet was deployed directly and not as an upgradable proxy. This meant the initialiser was not called and so the staking rewards contract was not assigned in the factory causing the contract to revert when it attempted to deploy due to trying to dereference a null staking rewards contract functionality.
• Add a parameter to allow reuse of a pre-existing token address instead of deploying a new one. This allows us to reuse the previous $SENT token on stagenet to simplify the network upgrade process.

[darcys22]

Can this be split so that the openzeppelin data and updating the hardcoded addresses in our scripts are separate from the new features?

Ill bring the reuse token contract and deploying as an upgradable proxy over into the PR i've got open