Add an upgrade() function to all L1 contracts

[maurelian]

Every L1 contract will get a new function alongside initialize():

function upgrade() external initialize {}

For most contracts it will be empty unless the forthcoming upgrade is adding new values to storage.

For contracts which have a non-empty upgrade() method
We will need a mechanism to identify when an L1 release has occurred which causes these functions to become a 'no-op'. They should be reset at that time.