better rpc error handling when rpc is behind requested block

[samlaf]

Our current error handling for rpc calls is not fine-grained enough.

See for eg https://github.com/Layr-Labs/eigenda-proxy/blob/main/verify/cert.go#L68-L71:

	confirmationBlockNumber := batchMetadata.GetConfirmationBlockNumber()
	confirmationBlockNumberBigInt := big.NewInt(0).SetInt64(int64(confirmationBlockNumber))
	_, err := cv.retrieveBatchMetadataHash(ctx, batchID, confirmationBlockNumberBigInt)
	if err != nil {
		return fmt.Errorf("batch not found onchain at supposedly confirmed block %d: %w", confirmationBlockNumber, err)
	}

retrieveBatchMetadataHash can actually return 2 very distinct errors:

1. when rpc node is behind confirmationBlockNumber (see here)
2. when contract was successfully queried at the confirmationBlockNumber, and the metadata was not present (see here)

Currently in both cases we still wrap the error returned from retrieveBatchMetadataHash in "batch not found onchain at block #", which is wrong. We should prob just have retrieveBatchMetadataHash write the entire error context in both cases, and then the outer callers shouldnt wrap the error at all.