feat: Add moderation and review stage to Event DB | NPG-0000

[coire1]

No description provided.

[Mr-Leshiy]

• added new table reviewer_level which represents a rewiew levels info as total reward percentage from the total cap and event to which it is assigned.
• added new columns to proposal_review table: assessor_level - reference to the reviewer_level table and reward_address - reward address for the reviewer
• added a new column review_rewards to the event table, which represents the total community reviewers pot.