feat(query): null type infer as Nullabel(String) by default in create as statement

[TCeason]

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Summary

• fixes: Feature: null type should infer as String Null by default in create as statement  #16794

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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This change is 

[what-the-diff]

PR Summary

• Enhancement in Schema Type Identification:
  We made an improvement to how our program recognizes the type of data in each column. It now uses a new technique that better caters to instances where the data type is not specified, by assuming it as a nullable string type.

• Removal of Redundant Testing Scenarios:
  We removed certain test scenarios that were unnecessary or unrelated. This improves the efficiency of our testing process.

• New Testing Scenarios Introduced:
  We introduced new tests that check how well our program can create a new table with specific attributes - an integer and a nullable string. They also verify whether the table creation commands are displaying as expected. This is to ensure our program is handling table creation tasks correctly and consistently.