union types and nullables can create unnecessary class suffixes (and related problems)

Describe the bug
In some valid specs, the use of anyOf, oneOf, nullable, and/or type as a list, can cause generated class names to have unnecessary suffixes (and, sometimes, for spurious extra copies of classes to appear). These problems seem to all ultimately come from the behavior of UnionProperty.

The problem cases are all included in the attached specs files. Looking at the code generated from these specs—

in both 3.0 & 3.1:

• ExampleModel.nullableObjectWithOneOf correctly has the type Union[MyObject, None, Unset].
• ExampleModel.inlineNullableObject generates a model class called ExampleModelInlineNullableObjectType0. It should be just ExampleModelInlineNullableObject, since there are no other named types for this property.
• Similarly, the MyEnum schema, which is a nullable enum, generates the class MyEnumType1 even though there is no Type0.
• The MyEnumWithExplicitType schema is the same as MyEnum except it specifically indicates type, and the result is a bit wilder: it generates enum classes MyEnumWithExplicitTypeType1, MyEnumWithExplicitType2Type1, and MyEnumWithExplicitType3Type1, all of which are exactly the same.

only applicable to 3.1:

• ExampleModel.nullableObjectWithExplicitTypes, which is the same as nullable_object_with_one_of except that it also (unnecessarily, but validly) specifies type: ["object", "null"], also works correctly.
• ExampleModel.one_of_enums_with_explicit_types, which combines a string enum with an int enum and specifies `type: ["string", "integer"], has the problem where three classes are created for each enum.

OpenAPI Spec Files
3.0: https://gist.github.com/eli-bl/7bea406525fb3b1452a71781ada5c1c0
3.1: https://gist.github.com/eli-bl/c03c88eb69312053e0122d1d8a06c2a0

Desktop (please complete the following information):

• OS: macOS 14.5
• Python Version: 3.8.15
• openapi-python-client version 0.21.5

从 UnionProperty 的行为入手，并根据链接的 OpenAPI 3.0 和 3.1 规范文件生成客户端。将生成的类名和重复模型与 issue 中描述的示例进行比较。当 nullable 和联合 schema 不再接收不必要的后缀，也不再创建相同的额外类时，即表示完成。