Take away block hash, block index dups processing script from migration to script

[vbaranov]

Relates to

Motivation

Take away block_hash, block_index duplicates processing script from migration to script as optional stuff since the probability of its necessity in migration is low but the time of execution is long. Thus, it is recommended to use it optionally if corresponding migration is failed due to {block_hash, block_index} pair duplicates.

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

[coveralls]

Pull Request Test Coverage Report for Build 8be2c84d-9e89-45b7-a83b-dac746c9e420

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.01%) to 75.248%

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Files with Coverage Reduction	New Missed Lines	%
apps/block_scout_web/lib/block_scout_web/controllers/chain/market_history_chart_controller.ex	1	78.57%

Totals
Change from base Build 4eeb35fe-dba3-426d-a52e-8fa890531245:	0.01%
Covered Lines:	5378
Relevant Lines:	7147

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💛 - Coveralls