feat(dot/parachain): create skeleton for bitfield distribution subsystem

[haikoschol]

Issue summary

• Create a new package called bitfielddistribution
• Define overseer messages
  • DistributeBitfield
    • relay parent hash
    • parachaintypes.UncheckedSignedAvailabilityBitfield
• Define network protocol messages (in the case of multiple versions, only handle the latest for now)
  • BitfieldProtocolMessage
    • only one possible value, with the same content as DistributeBitfield overseer message
• Create a struct called BitfieldDistribution and implement the Subsystem interface on it
• Register bitfield distribution subsystem with overseer
• Create (empty) methods to handle the following messages:
  • DistributeBitfield
  • network bridge events
    • PeerConnected
    • PeerDisconnected
    • NewGossipTopology
    • PeerViewChanged
    • OurViewChanged
    • PeerMessage (payload: parachaintypes.UncheckedSignedAvailabilityBitfield)
    • UpdatedAuthorityIds
  • overseer signals
    • ActiveLeavesUpdate
• Forward the above messages to the bitfield distribution subsystem from overseer
• Add tests

Other information and links

Look at other skeleton PRs to get an idea of what to code and what will become and TODO and a new issue

• feat(dot/parachain): Implement candidate backing skeleton #3497
• feat(parachain): availability store skeleton #3521
• collator protocol skeleton #3512