Release v0.4.0

Fixed

• Interactions with the ledger service are now async. This fixes situations in which expensive ledger operations could starve the state machine loop.
• Ledger synchronization issue that happens when synchronizing the node during the second epoch.
• Correctly handle the situation in which the best tip changes during staged ledger reconstruction, causing the reconstruct to produce a stale result.
• Various edge cases in p2p layer (error propagation, disconnection, self-connection).

Added

• Support for identify protocol.
• P2P layer testing framework.
• Frontend: Block production page.

Removed

• Removed rust-libp2p based code, in favor of our own libp2p implementation.