Add reflection configuration for Actuator endpoints

[bclozel]

After the fix for #992, we're seeing that the actuator-webmvc sample fails with the following behavior:

• all 15 endpoints are detected by actuator
• the CustomNoComponent endpoint is created as a bean as expected
• fetching localhost:8080/actuator/customnc fails with a 404

It seems that reflection information is registered for the Custom endpoint, because it is annotated with @Component:

  {
    "name": "com.example.demo.Custom",
    "allDeclaredFields": true,
    "allDeclaredConstructors": true,
    "allDeclaredMethods": true,
    "allPublicMethods": true,
    "allDeclaredClasses": true,
    "methods": [
      {
        "name": "<init>",
        "parameterTypes": []
      }
    ]
  },

On the other hand, nothing is registered for the CustomNoComponent endpoint - actuator cannot look for a @ReadOperation-annotated method and won't register that as an endpoint.

[snicoll]

Fixed by 7298292