fix: expand DataValue::Utf8 so that it can correspond to Char and Varchar respectively.

[KKould]

What problem does this PR solve?

originally, both LogicalType::Char and LogicalType::Varchar used DataValue::Utf8, but DataValue::Utf8 does not know its own logical_type

Code changes

• Has Rust code change
• Has CI related scripts change

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Note for reviewer

[crwen]

Is this a necessary change? can you give me some situations

[KKould]

Is this a necessary change? can you give me some situations

This pr is mainly due to the DataValue::logical_type method, because when selecting LogicalType::Char and LogicalType::Varchar to share DataValue::Utf8 in the previous pr: #174, the conversion from DataValue to LogicalType was ignored, which may cause LogicalType::Char to be converted to DataValue:: Utf8 and then converted to LogicalType::Varchar, potentially causing many problems