[DRAFT] Make the return type of lambda functions inferrable

[yuancu]

Description

Status: blocked by #4892 , diff can be viewed from 42a7386

Lambda function is used in transform function:

sql/docs/user/ppl/functions/collection.md

Lines 157 to 171 in 1192376

	## TRANSFORM
	### Description
	Usage: `transform(array, function)` transform the element of array one by one using lambda. The lambda function can accept one single input or two input. If the lambda accepts two argument, the second one is the index of element in array.
	Argument type: array:ARRAY, function:LAMBDA
	Return type: ARRAY
	Example
	```ppl
	source=people
	| eval array = array(1, -2, 3), result = transform(array, x -> x + 2)
	| fields result
	| head 1
	```

When defining a lambda function, it's parameter type needs to be explicitly specified. Otherwise, the parameters will be deemed of type ANY per the constructor of SqlLambdaScope, blocking the subsequent type inference.

public SqlLambdaScope(
    SqlValidatorScope parent, SqlLambda lambdaExpr) {
  super(parent);
  this.lambdaExpr = lambdaExpr;

  // default parameter type is ANY
  final RelDataType any =
      validator.typeFactory.createTypeWithNullability(
          validator.typeFactory.createSqlType(SqlTypeName.ANY), true);
  parameterTypes = new HashMap<>();
  lambdaExpr.getParameters().forEach(param -> parameterTypes.put(param.toString(), any));
}

For the expressiontransform(array, (x, i) -> x + i) , x should be of array's element type, while i should be of integer type (it represents index). This PR passes on this semantic via a SqlOperandTypeInference definition.

TODOs:

• Make lambda return type inferrable
• Yaml test, Explain IT, integration test

Related Issues

Resolves #4972

Check List

• New functionality includes testing.
• New functionality has been documented.
• New functionality has javadoc added.
• New functionality has a user manual doc added.
• New PPL command checklist all confirmed.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff or -s.
• Public documentation issue/PR created.

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