deduplicate coin history records by delta

[ayrat555]

On coin history page we show records that are found
in the db. Since we may fetch a lot of duplicated balances
for the same address if its balance is not changes for
multiple blocks.

This PR adds deduplication by delta value to remove duplication.

fixes #2565

Changelog

• deduplicate coin history records by delta

[coveralls]

Pull Request Test Coverage Report for Build 603c30bf-58f2-45ee-8f37-c3fbd2696725

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.2%) to 78.999%

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Files with Coverage Reduction	New Missed Lines	%
apps/indexer/lib/indexer/fetcher/internal_transaction.ex	2	60.66%

Totals
Change from base Build c31ac9df-9686-4cbb-86da-b46b40fe0eba:	0.2%
Covered Lines:	5195
Relevant Lines:	6576

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💛 - Coveralls

[vbaranov]

@ayrat555

Deduplication significantly slowed down coin balance history page. Please check /address/0xc8dfcec53ab1102a38e8f96be8eba37fc5340c99/coin_balances.

We show the changes in the 3 months range on the chart. Which conditions are provided in the query to get coin balance history? Could post a link to the query here? I suppose we should get data in a query in the same range if it is not so.

[ayrat555]

@vbaranov I compared page loading with and without deduplication. they seem it's the same.
chart items query - https://github.com/poanetwork/blockscout/blob/master/apps/explorer/lib/explorer/chain/address/coin_balance.ex#L92
coin balances list query -
https://github.com/poanetwork/blockscout/blob/master/apps/explorer/lib/explorer/chain/address/coin_balance.ex#L74

[vbaranov]

Ok, it looks like it was a temporary issue. Times are comparatively equal.