When a shard becomes search active then trigger a refresh instead of waiting for the next scheduled refresh.
The `IndexShard#awaitShardSearchActive(...)` method registers a refresh listener and then often waits for the refresh scheduler to trigger a refresh. By default this is one second. In order to avoid increasing the query time of the Search API, the mentioned method should trigger a refresh instead for waiting it to happen.

As part of this change we also need to disable the refresh scheduler completely. Otherwise we run at risk of running two refreshes next after each other. One triggered from making shard search active and one from the refresh scheduler.  



server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
MappingLookup mappingLookup = mapperService.mappingLookup();
        if (mappingLookup.hasMappings() == false) {
            return GetResult.NOT_EXISTS;
        }
        if (indexSettings.getIndexVersionCreated().isLegacyIndexVersion()) {
            throw new IllegalStateException("get operations not allowed on a legacy index");
        }
        if (translogOnly) {
            return getEngine().getFromTranslog(get, mappingLookup, mapperService.documentParser(), this::wrapSearcher);
        }
        return getEngine().get(get, mappingLookup, mapperService.documentParser(), this::wrapSearcher);
    }
    /**
     * Writes all indexing changes to disk and opens a new searcher reflecting all changes.  This can throw {@link AlreadyClosedException}.
     */
    public Engine.RefreshResult refresh(String source) {
        verifyNotClosed();
        logger.trace("refresh with source [{}]", source);
        return getEngine().refresh(source);
    }
    public void externalRefresh(String source, ActionListener<Engine.RefreshResult> listener) {
        verifyNotClosed();
        getEngine().externalRefresh(source, listener);
    }
    /**
     * Returns how many bytes we are currently moving from heap to disk
     */
    public long getWritingBytes() {
        Engine engine = getEngineOrNull();
        if (engine == null) {