[Client in a web API] Port middleware services to the client library

[tusmester]

Port the generalized services, extensions, and helper methods from TFS to the client package.

• refactor service registration methods to use the correct APIs and scopes
• Add dedicated service methods for the web API scenario

For example:

public interface IRepositoryService
{
    public Task<IRepository> GetUserRepositoryAsync(CancellationToken cancel);
    public Task<IRepository> GetVisitorRepositoryAsync(CancellationToken cancel);
    public Task<IRepository> GetAdminRepositoryAsync(CancellationToken cancel);
}