Previously, if an injection point used a qualifier, `MockBean` and
`SpyBean` couldn't be used to mock/spy it as there was no way to
specify that qualifier information.

This commit now detects qualifier information on the injection point
and associate it with the created `BeanDefintion`. If one wants to
mock a bean that is qualified with `@Qualifier("foo")`, the definition
of the mock should be as follows:

```
public class MyTest {

	@MockBean
	@Qualifier("foo")
	private ExampleService service;
}
```

As a side effect, it is now possible to mock a service by type even if
there are multiple instances of that type in the application context. The
provided qualifier information is used to determine the right candidate
and the proper bean definition is replaced accordingly.

Closes gh-6753