Introduce event log

[shuse2]

LIP

Add events root to block headers

Motivation

Introduce event log to the blockchain protocol. During the block and transaction execution, developer should be able to add log, which will be emitted to the external system when successfully block is executed.
This will enable the intermediate step of a transaction or cross chain message to be part of the blockchain protocol

Tasks

• Update EventQueue interface and application config #7124
• Update lisk-chain to save/delete events together with block #7125
• Add chain_getEvents and chain_proveEvents endpoints #7126
• Update block processing to handle events #7127