Darwinia2.0 and ETH updates

[furoxr]

TODO:

• [x] Update client-darwinia

Updates:

1. Remove execution layer relay service
2. Follow updates of ETH light client spec
3. Optimize gas limit and gas price of transactions

Fix:

1. ECDSA client can not reconnect after connection lost
2. Service stuck when waiting for transaction confirmation

Test on Pangolin2 and Goerli:

• https://goerli.etherscan.io/address/0x573749ffee40b3aa6c080144d4071847c51b5c33

Related issue and PR:

• https://github.com/darwinia-network/bridger/issues/571
• https://github.com/darwinia-network/darwinia-messages-sol/pull/321
• https://github.com/darwinia-network/darwinia-messages-sol/pull/308
• https://github.com/darwinia-network/darwinia-messages-sol/pull/329