We would like to revisit the `Authentication` class to make it provide better and easier to use interface to the consumers. 

#79809 enables run-as for all authentication schemes in addition to `realm` which is already supported. This adds more complexity to an `Authentication` object and how it should be used. For an example, building the role associated to an user now has to consider whether the user is the authenticated user or run-as user and the authentication scheme of the authenticated user. The existing `Authentication` class can answer all these question today. But its interface and internals are not aligned for these questions and the usage is error prone. For example, the `Authentication` object itself does not know whether the user has run-as. This information is kept by the `User` object. If the `User` object has an `authenticatedUser`, it's the run-as user. Otherwise it is not. But the information about realms for each `User` is directly kept in `Authentication`. Therefore, for full picture, the caller must check both `User` and `Authentication` realms and understands the nuance of their differenent combinations. 

- [x] Refactor CompositeRolesStore to separate roleDescriptors resolving (#80926)
- [ ] Move effective role descriptor checking from Resolver to CompositeRolesStore
- [x] https://github.com/elastic/elasticsearch/issues/81192
- [ ] Replace Authentication with AuthenticationContext in places other than CompositeRolesStore
x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authc/Authentication.java
public String toString() {
            if (domain != null) {
                return "{Realm[" + type + "." + name + "] under Domain[" + domain.name() + "] on Node[" + nodeName + "]}";
            } else {
                return "{Realm[" + type + "." + name + "] on Node[" + nodeName + "]}";
            }
        }
        static RealmRef newInternalAttachRealmRef(String nodeName) {
            
            return new Authentication.RealmRef(ATTACH_REALM_NAME, ATTACH_REALM_TYPE, nodeName, null);
        }
        static RealmRef newInternalFallbackRealmRef(String nodeName) {
            
            RealmRef realmRef = new RealmRef(FALLBACK_REALM_NAME, FALLBACK_REALM_TYPE, nodeName, null);
            return realmRef;
        }
        static RealmRef newAnonymousRealmRef(String nodeName) {
            
            return new Authentication.RealmRef(ANONYMOUS_REALM_NAME, ANONYMOUS_REALM_TYPE, nodeName, null);
        }
        static RealmRef newServiceAccountRealmRef(String nodeName) {
            
            return new Authentication.RealmRef(ServiceAccountSettings.REALM_NAME, ServiceAccountSettings.REALM_TYPE, nodeName, null);
        }
        static RealmRef newApiKeyRealmRef(String nodeName) {
            
            return new RealmRef(API_KEY_REALM_NAME, API_KEY_REALM_TYPE, nodeName, null);
        }
    }
    public static boolean isFileOrNativeRealm(String realmType) {