Ornamentation

This patch-release supports an event subscription from dBFT and improves the
PreBlock construction about Envelope transaction handling. Since the Cancun
and Prague upgrades work on TestNet quite well, this version also schedules
the same upgrades for MainNet.

This version is fully compatible with v0.5.0 and does not require node
resynchronization. For TestNet nodes no configuration changes are required on
upgrade (comparing to v0.5.0). For MainNet nodes the DB reinitialization is
required with the updated genesis configuration since Cancun and Prague
forks are enabled. Follow the instructions below to upgrade your node from
v0.5.0 to v0.5.1:

1. Download new binary and new genesis configuration file from the release page.
2. Gracefully stop the node.
3. Replace the old binary with the new binary.
4. For MainNet nodes only: don't remove DB; reinitialize DB using new binary and
   new genesis configuration file with the following command:

   ./geth init --datadir ./node-datadir ./config/genesis.json
   

5. Start the node.

New features:

• support a real-time event subscription about Envelopes (#528, #530)

Behaviour changes:

• Cancun fork is enabled at timestamp 1763000000 on MainNet (#531)
• Prague fork is enabled at timestamp 1763000000 on MainNet (#531)

Improvements:

• refactor PreBlock handling to avoid unexpected Envelope revert (#528)
• update system contract documentation about Message Bridge (#529)