fix(@nestjs/graphql): validate registerEnumType/createUnionType options eagerly

[yogeshwaran-c]

Summary

• Throw a descriptive error when registerEnumType or createUnionType are called without an options object, without a non-empty name, or (for unions) without a types function.
• Validation runs at registration time so the stack trace points at the offending call site instead of LazyMetadataStorage.load -> addEnumMetadata deep in the schema-builder pipeline.

Bug

The TypeScript signatures mark these inputs as optional/permissive but the lazy callbacks dereference them unguarded. Calling registerEnumType(MyEnum) therefore blew up with:

TypeError: Cannot read properties of undefined (reading 'name')
  at LazyMetadataStorage.load
  at GraphQLSchemaFactory.create
  ...

createUnionType({ types: () => [...] }) (no name) silently registered a Symbol(undefined) and surfaced as a "Schema must have a name" failure inside graphql-js much later.

Fix

• registerEnumType: require options and require options.name to be a non-empty string.
• createUnionType: same name check, plus typeof options.types === 'function'.
• Both errors now identify the failing API and show a corrected example in the message.

Test plan

• New spec tests/type-factories/enum-union-options-validation.spec.ts covers each missing-input branch and the happy path.
• tests/schema-builder/**, tests/type-helpers/**, tests/type-factories/** continue to pass.