[META] Update Mainnet Release

[fredo]

Problem Description

Some updates to the upcoming mainnet release are already known and will be tracked here for the first update (roughly 2 weeks after the mainnet release)

• Update to synapse 1.34.0
• re enable purger using the PFS as source
  • revert 4de644b
  • Return last seen timestamp raiden-services#991
  • refactor purger to use PFS
• new docker-compose setup due to the removed limitations by 1.34.0 (@ulope)
• Mechanism to periodically update federation whitelist