Replace epochTime with genesis block timestamp

[shuse2]

Description

• Remove the epoch time from the config
• Update the slot calculation in lisk-chain to use genesis block timestamp instead of epoch time.

The slot number will be calculated as:

Math.floor((slotTime - genesisBlock.timestamp) / this._interval);

Where slotTime can be any unix time and interval would be the block time which is default to 10s.

Motivation

• With the new LIP, the epoch time difference is removed.

Acceptance Criteria

• All tests are updated not to use the epoch time

Additional Information

The related information can be found on https://github.com/LiskHQ/lips/blob/master/proposals/lip-0034.md#block-processing

This way, the genesis block timestamp defines the block slots of the blockchain as [b.header.timestamp+BLOCK_SLOT_LENGTH, b.header.timestamp + 2*BLOCK_SLOT_LENGTH), [b.header.timestamp + 2*BLOCK_SLOT_LENGTH, b.header.timestamp + 3*BLOCK_SLOT_LENGTH), and so on.

Related issues #5234

• lisk-chain/src/slots.ts contains the main logic of the epochTime usage
• epochTime needs to be removed from framework/src/application/schema/application_config_schema.ts, and all other usages