### Description

In [siren federate](https://siren.io/federate/) we extend the `SearchService` to create `SearchContext` instances. In 8.8 this is not possible anymore because the `createContext` method takes the `ResultsType` enum which is package private.

https://github.com/elastic/elasticsearch/blob/b640c217cccab67dce7d954bc92b6b519c102b16/server/src/main/java/org/elasticsearch/search/SearchService.java#L992-L998

In order to be able to keep on calling that method from another package, the visibility of the enum `ResultsType` should be increased to `protected`.
server/src/main/java/org/elasticsearch/search/SearchService.java
if (shard.getLastKnownGlobalCheckpoint() >= waitForCheckpoint) {
                        searchReady();
                        return;
                    }
                    shard.addGlobalCheckpointListener(waitForCheckpoint, new GlobalCheckpointListeners.GlobalCheckpointListener() {
                        @Override
                        public Executor executor() {
                            return threadPool.executor(Names.SAME);
                        }
                        @Override
                        public void accept(long g, Exception e) {
                            if (g != UNASSIGNED_SEQ_NO) {
                                assert waitForCheckpoint <= g
                                    : shard.shardId() + " only advanced to [" + g + "] while waiting for [" + waitForCheckpoint + "]";
                                searchReady();
                            } else {
                                assert e != null;
                                
                                if (e instanceof TimeoutException == false) {
                                    onFailure(e);
                                }
                            }
                        }
                    }, NO_TIMEOUT.equals(timeout) == false ? null : timeout);
                }
                @Override
                public void onFailure(Exception e) {
                    if (isDone.compareAndSet(false, true)) {