Implement unlock command for DPoS module

[mehmetegemen]

Description

Implement a token unlocking command in unlock.ts in the commands folder as in the LIP (https://research.lisk.com/t/define-state-and-state-transitions-of-dpos-module/320#unlock-52)

• Define command id as in the LIP. Command has no params so an empty schema is required.
• Define command name as unlockToken
• Implement execute hook as in the LIP

Acceptance Criteria

• Possible scenarios are tested in the unit test for execute hook
• All logic exist in the previous DPoS module
• keep in mind unlockHeight is not considered on unlockToken transaction during punishment #6793