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

https://github.com/near/near-indexer-for-explorer/blob/08dfbe7d8f3a3e49ee42dd0720b444e8520cc147/src/main.rs#L86-L91

[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