Call and use ConfigureServices if exists

Currently only looks for signatures like this:

public [static] void ConfigureServices(IServiceCollection services, ...)

Will add support for more overloads like one that returns a IServiceProvider next
Design-time tooling such as Migrations and Scaffolding will need a public way to invoke ConfigureServices (and not Configure) from the outside. Should each tool implement its own reflection logic to find the class and method or is there something we can put here (or somewhere else) to make this reusable?