feat(schema): add directives support to registerEnumType

[jlang-ih]

• Add optional directives: string[] parameter to registerEnumType, enabling directive support on enum types (e.g. directives: ["@cacheControl(maxAge: 30)"])
• Follow the same directive handling pattern used by ObjectType, InterfaceType, and InputType — directive strings are converted to DirectiveMetadata, processed through getEnumTypeDefinitionNode, and emitted as astNode on the GraphQLEnumType
• Add tests covering simple directives, directives with arguments, and multiple directives on a single enum

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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