Reduce BlocksTransactionsMismatch memory footprint

[pasqu4le]

closes #2234

Changelog

Enhancements

This PR reduces the memory footprint of the BlocksTransactionsMismatch temporary fetcher by requesting only the block hash instead of the whole block.

Checklist for your 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 if necessary

[coveralls]

Pull Request Test Coverage Report for Build 07390a12-adea-459b-835c-78d93fd99c5b

• 0 of 5 (0.0%) changed or added relevant lines in 1 file are covered.
• 9 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.1%) to 80.991%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
apps/indexer/lib/indexer/temporary/blocks_transactions_mismatch.ex	0	5	0.0%

Files with Coverage Reduction	New Missed Lines	%
apps/block_scout_web/lib/block_scout_web/channels/exchange_rate_channel.ex	1	50.0%
apps/indexer/lib/indexer/fetcher/token.ex	1	78.57%
apps/indexer/lib/indexer/fetcher/internal_transaction.ex	2	58.62%
apps/indexer/lib/indexer/fetcher/token_balance.ex	2	87.1%
apps/indexer/lib/indexer/block/fetcher.ex	3	88.0%

Totals
Change from base Build f7af39be-7886-42ee-a941-114a4933d42c:	-0.1%
Covered Lines:	5036
Relevant Lines:	6218

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💛 - Coveralls