Update dependency proxy controllers namespace

Proposal

In !64363 (merged) we refactored to include Groups::DependencyProxy::ApplicationController. The other dependency proxy controllers could benefit from common namespacing and possibly being renamed:

Current name	Proposed name
Groups::DependencyProxyAuthController	Groups::DependencyProxy::AuthController
Groups::DependencyProxyForContainersController	Groups::DependencyProxy::ApiController or Groups::DependencyProxy::ImageController ?

This issue originates from this comment