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
Authentication authentication = new Authentication(
            serviceAccountUser,
            authenticatedBy,
            null,
            Version.CURRENT,
            AuthenticationType.TOKEN,
            metadata
        );
        assert false == authentication.isAssignedToDomain();
        return authentication;
    }
    public static Authentication newRealmAuthentication(User user, RealmRef realmRef) {
        
        assert false == user instanceof RunAsUser;
        Authentication authentication = new Authentication(user, realmRef, null, Version.CURRENT, AuthenticationType.REALM, Map.of());
        assert false == authentication.isServiceAccount();
        assert false == authentication.isApiKey();
        assert false == authentication.isAuthenticatedInternally();
        assert false == authentication.isAuthenticatedAnonymously();
        return authentication;
    }
    public static Authentication newApiKeyAuthentication(AuthenticationResult<User> authResult, String nodeName) {
        assert authResult.isAuthenticated() : "API Key authn result must be successful";
        final User apiKeyUser = authResult.getValue();
        assert false == apiKeyUser instanceof RunAsUser;
        assert apiKeyUser.roles().length == 0 : "The user associated to an API key authentication must have no role";
        final Authentication.RealmRef authenticatedBy = newApiKeyRealmRef(nodeName);
        Authentication authentication = new Authentication(
            apiKeyUser,
            authenticatedBy,