Describe the bug
ExecutableNormalizedField.forEachFieldDefinition() and getOneFieldDefinition() call type.getField(fieldName) directly, bypassing the schema's configured GraphqlFieldVisibility.

This is inconsistent with other parts of graphql-java (validation, execution) that respect field visibility, and causes issues when:

A custom GraphqlFieldVisibility provides field definitions that differ from what's in the schema type (e.g., placeholder fields, virtual fields, or dynamically-computed fields)
Application code accesses DataFetchingEnvironment.getSelectionSet().getFields() in a DataFetcher
Normalization fails with "No field X found for type Y" because it bypasses the visibility

To Reproduce

1. Configure a custom GraphqlFieldVisibility that provides virtual/placeholder fields
2. Execute a query that includes a field only available through the visibility
3. Access DataFetchingEnvironment.getSelectionSet().getFields() in a DataFetcher
4. Normalization fails because ExecutableNormalizedField.forEachFieldDefinition() calls type.getField() directly

** Expected Behavior**
ExecutableNormalizedField should use the schema's field visibility when looking up field definitions, consistent with how validation and execution work.

PR is raised here