[storage] Interface Refactor + Test Cleanup

[patrick-ogrady]

To make it easier to test modules, we've decided to refactor the storage package into storage/database and storage/modules. This allows us to use generated mocks when testing storage/modules (removes a circular dependency that prohibited use of interfaces defined in storage) instead of relying on hand-rolled mocks 🤮 .

This PR adds no new functionality!

Changes

• refactor storage into database, modules, encoder, and errors
• fix existing tests from refactor
• use mocks for tests instead of hand-rolled mocks
  • BalanceStorage
  • BroadcastStorage
  • CoinStorage
• fix import ordering
  • run goimports-reviser in check-gen

[coveralls]

Pull Request Test Coverage Report for Build 12479

• 87 of 313 (27.8%) changed or added relevant lines in 11 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.4%) to 78.203%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
storage/modules/balance_storage.go	11	12	91.67%
storage/database/badger_database_configuration.go	4	6	66.67%
storage/modules/counter_storage.go	0	2	0.0%
storage/modules/coin_storage.go	11	32	34.38%
storage/modules/key_storage.go	5	29	17.24%
storage/database/badger_database.go	13	40	32.5%
storage/modules/broadcast_storage.go	1	32	3.13%
storage/modules/job_storage.go	4	37	10.81%
storage/modules/block_storage.go	30	65	46.15%
storage/encoder/encoder.go	0	50	0.0%

Totals
Change from base Build 12213:	-0.4%
Covered Lines:	7771
Relevant Lines:	9937

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💛 - Coveralls