fix(query): change default format_null_as_str to false

[everpcpc]

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Summary

We have already support json null in all drivers.
Changing this default to false, then we could correctly handle Nullable(String) with 'NULL' in response.

• for: bug: nullable response for varchar bendsql#626

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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