Add primary keys for diff tables

[vbaranov]

Motivation

Missing primary keys complicate DB migration to other DB type.

Changelog

Add primary keys repeating already existing unique indexes for the next tables (and remove those unique indexes):

• public.block_rewards
• public.address_coin_balances_daily
• public.emission_rewards
• public.transaction_forks
• public.address_coin_balances

Add serial column for address_names table and set it as primary_key

Checklist for your Pull Request (PR)

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so by submitting a PR to https://github.com/blockscout/docs
• If I added/changed/removed ENV var, I submitted a PR to https://github.com/blockscout/docs to update the list of env vars at https://github.com/blockscout/docs/blob/master/for-developers/information-and-settings/env-variables.md and I updated the version to master in the Version column. Changes will be reflected in this table: https://docs.blockscout.com/for-developers/information-and-settings/env-variables.
• If I add new indices into DB, I checked, that they are not redundant with PGHero or other tools