Update interface client code to replace `GroupsMetadata.loadClass` calls
with `ClassUtils.resolveClassName` passing in the bean class loader.
Since the bean class loader in injected after construction, some minor
refactoring has been applied to `HttpServiceProxyRegistryFactoryBean`.
The class now stores `GroupsMetadata` and only loads the types in
in `afterPropertiesSet`.
The `HttpServiceProxyFactory` class has also been updated to ensure
that the proxy is created using the class loader of the service
type, rather than the thread context class loader.
Fixes gh-34846
abbee1a050