Migrate UDF operator transformers based on JSON-infra into transformers based on native Java code

[yiqiangin]

In order to migrate all the transformers in which any of operatorTransformer, operandTransformer and resultTransformer is defined as a JSON string into the transformers which define the transformation rule in native Java code, the following code changes are made in this PR:

• Adding some classes to implement the transformers which extends SignatureBasedConditionSqlCallTransformer and the specific transformation logic is defined as native Java code including
  • DateDiffOperatorTransformer
  • DateSubOperatorTransformer
  • DateAddOperatorTransformer
  • DecodeOperatorTransformer
  • RegexpExtractOperatorTransformer
  • ModOperatorTransformer
  • TruncateOperatorTransformer
  • RandomIntegerOperatorWithTwoOperandsTransformer
  • RandomOperatorWithOneOperandTransformer
• Removing the code related to operatorTransformer, operandTransformer and resultTransformer defined as JSON strings out of the class of SignatureBasedConditionSqlCallTransformer

To be noted that this PR is based on PR #349