Description

• Changed return types from fully qualified names to short names.
• Updated ServiceInterface to be imported from within the ClientImpl class, rather than as a separate class import (TestInterfaceClientImpl.TestInterfaceClientService).
• Removed CodegenUtil as its methods are no longer needed due to return type updates.
• Modified getNewInstance to use HttpPipeline and Serializer input parameters.
• Made miscellaneous updates including adding Javadoc, cleaning up unused methods, and adjusting modifiers.
• Added entityType processing in response body handling instead of relying on strings.
• Switched to using Coreutils for parameterized type creation.
• Fixed generic type method parameter to correctly add generic arguments, changing from List to List<String>.
• Fix issue where null query parameters are added to the host string.

Generated Impl

Closes: #44270