[Gnosis] Balancer HF

[yperbasis]

Implements https://hackmd.io/@filoozom/rycoQITlWl. However, censoringSchedule in JSON config is implemented as a map with timestamp keys rather than an array.

Provisionally sets BALANCER_HARDFORK_TIMESTAMP to 1764760000.

TODO:

• Replace 1764760000 (two occurrences) in gnosis.json with the real value.
• Remove 0xd573BC65602d4Ea7e4ABe707c15FB5FC461CE0F1 from balancerRewriteBytecode (only required for the shadow fork)