[fix][io][branch-3.0]Pulsar-SQL: Fix classcast ex when decode decimal value

[poorbarcode]

Motivation

The original implementation of decoding was introduced by #15687, The implementation is as follows

String textValue = value.isValueNode() ? value.asText() : value.toString();
if (type instanceof DecimalType) {
    textValue = textValue.replace(".", "");
    BigInteger bigInteger = new BigInteger(textValue);
    return Decimals.encodeUnscaledValue(bigInteger);
}

#20016 introduced a break change, which added a classcast from object to DecimalNode, The implementation was changed to as follows

// value is typed "Object", the actual type is a JsonNode
final DecimalNode node = (DecimalNode) value;
type.writeObject(blockBuilder, Int128.valueOf(node.asText().replace(".", "")));

Modifications

Revert the implementation to the original.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

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[poorbarcode]

Please do not merge this PR so far, I am fixing an issue

[poorbarcode]

Please do not merge this PR so far, I am fixing an issue

Sorry, I tested with the wrong code, so there is no issue