feat(sql): support nested lambda functions

[bohutang]

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Summary

Remove the restriction that prevented lambda functions from being used inside other lambda functions, aligning with Snowflake's TRANSFORM behavior.

Problem: Multi-level nested array transformations (e.g. events[*].attributes[*].value.stringValue) required verbose LATERAL FLATTEN + GROUP BY workarounds because json_array_transform could not be nested inside another json_array_transform.

Root cause: A conservative guard added in the initial lambda implementation (PR #12217, 2023) blocked all lambda-in-lambda usage at the type checker level. However, the evaluator already supports recursive execution — eval_lambda_block creates a new Evaluator that naturally handles nested LambdaFunctionCall nodes.

Fix:

1. Remove the type checker guard that rejected nested lambdas.
2. Implement parameter shadowing via UnqualifiedWildcardInVisible — when a lambda parameter has the same name as an outer column, the outer column is hidden from unqualified lookup but remains accessible via qualified reference (e.g. table.column). This preserves backward compatibility with existing queries.

After this change:

SELECT json_array_transform(
  raw_data:events,
  e -> object_insert(e, 'attributes',
    json_array_transform(e:attributes, a ->
      CASE WHEN a:key::string = 'body'
        THEN object_insert(a, 'value',
          object_insert(a:value, 'stringValue',
            to_variant(left(a:value:stringValue::string, 50)), true), true)
        ELSE a END
    ), true)
) FROM traces_table;

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test

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):

---

This change is 

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• tag: pr-19936-f398a33-1780055850

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