Compression + Storage Optimization

[patrick-ogrady]

This PR introduces a few storage optimizations that significantly improve the performance of the entire storage package in the real world. Many of these optimizations were performed while working on rosetta-bitcoin (soon to be released).

The most noticeable change is that all data saved to disk is now first compressed by https://github.com/facebook/zstd.

Warning

This PR changes how all data is stored. You will need to delete any previously saved data when upgrading.

Future PR

Make it easy for users to train a zstd dictionary to further increase compression ratio (on small data, has been shown to 4-8x compression ratio): https://github.com/facebook/zstd#the-case-for-small-data-compression

[coveralls]

Pull Request Test Coverage Report for Build 4754

• 154 of 182 (84.62%) changed or added relevant lines in 7 files are covered.
• 151 unchanged lines in 6 files lost coverage.
• Overall coverage decreased (-0.02%) to 77.033%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
storage/balance_storage.go	1	2	50.0%
storage/badger_storage.go	21	23	91.3%
storage/coin_storage.go	24	27	88.89%
storage/utils.go	10	16	62.5%
storage/block_storage.go	96	112	85.71%

Files with Coverage Reduction	New Missed Lines	%
reconciler/reconciler.go	1	84.18%
storage/block_storage.go	3	69.53%
constructor/worker.go	19	85.61%
storage/coin_storage.go	26	72.73%
utils/utils.go	44	51.35%
fetcher/construction.go	58	0%

Totals
Change from base Build 4644:	-0.02%
Covered Lines:	4102
Relevant Lines:	5325

---

💛 - Coveralls

[yfl92]

LGTM