Suggestion to make transactions and receipts adapters to sequential way

[khorolets]

Recent testnet load with 200+ transactions and 300+ receipts were lagging.

I really think this code causes the retry with a too heavy payload and we should try to avoid it

near-indexer-for-explorer/src/main.rs

Lines 86 to 91 in 08dfbe7

	// We can process transactions and receipts in parallel
	// because most of receipts depend on transactions from previous blocks,
	// so we can save up some time here.
	// In case of local receipts (they are stored in the same block with corresponding transaction),
	// we hope retry logic will cover it fine
	try_join!(transactions_future, receipts_future)?;

[khorolets]

@telezhnaya what do you think?

/cc @frol

[frol]

@khorolets Let's measure it on the specific block with and without concurrency and then make the final decision.

[frol]

Just for the future investigation, the recent blocks that caused slowdowns on mainnet are around #61617473