Service instantiation via another service

[eledhwen]

Similarly to what can already be done with static method calls, it should be made possible to instantiate a service by calling an instance method.

So, for the recall, a direct declaration looks like this, it will create an instance using a constructor with the provided arguments:

my_service:
    class: "com.mypackage.MyClass"
    constructor:
        - "some_argument"
        - 123

A static method declaration looks like this, it will call the someMethod method over the MyClass class with the provided arguments:

my_service:
    class: "com.mypackage.MyClass"
    method: "someMethod"
    arguments:
        - "some_argument"
        - 123

In the same spirit, instance method declaration could look like this:

my_service:
    service: "@my_other_service"
    method: "someMethod"
    arguments:
        - "some_argument"
        - 123