### Description

**Description**

We have been conducting user research on the copy and other aspects of the health API and have a few concrete copy suggestions from the user interviews. 

**StableMasterHealthIndicator**

1. We have user action `UNSTABLE_MASTER_DEPLOYMENT_MANAGEMENT_IMPACT` ([line](https://github.com/elastic/elasticsearch/blob/master/server/src/main/java/org/elasticsearch/cluster/coordination/StableMasterHealthIndicatorService.java#L62). I propose

_Before_: "Scheduled tasks such as Watcher, ILM, and SLM will not work. The _cat APIs will not work." 

_After_:  "Scheduled tasks such as Watcher, Index Lifecycle Management and Snapshot Lifecycle Management will not ...."  instead of using the abbreviations. Some users might not know the terms but at least this gives them more to search on and learn from. 

2. The `UNSTABLE_MASTER_BACKUP_IMPACT` ([line](https://github.com/elastic/elasticsearch/blob/100f5acd345dd13d8c8d17b93392d4b217bc50a2/server/src/main/java/org/elasticsearch/cluster/coordination/StableMasterHealthIndicatorService.java#L64)), I propose making the impact even clearer in laymen terms. 

_Before_: "Snapshot and restore will not work. Searchable snapshots cannot be mounted."
_After_: "Snapshot and restore will not work, your data will not be backed up. Searchable snapshots cannot be mounted, search on backup data will not return results."

I propose we do the same for the messages in the `SlmHealthIndicatorService`, and use the unabbreviated messages where shown to users. 
server/src/main/java/org/elasticsearch/cluster/coordination/StableMasterHealthIndicatorService.java
* (1) no node is elected master, (2) this node is not master eligible, (3) some node is master eligible, (4) we ask a master-eligible node
 * to run this indicator, and (5) it comes back with a result that is not RED.
 * Since this indicator needs to be able to run when there is no master at all, it does not depend on the dedicated health node (which
 * requires the existence of a master).
 */
public class StableMasterHealthIndicatorService implements HealthIndicatorService {
    public static final String NAME = "master_is_stable";
    public static final String GET_HELP_GUIDE = "https://ela.st/getting-help";
    public static final Diagnosis CONTACT_SUPPORT_USER_ACTION = new Diagnosis(
        new Diagnosis.Definition(
            NAME,
            "contact_support",
            "The Elasticsearch cluster does not have a stable master node.",
            "Get help at " + GET_HELP_GUIDE,
            GET_HELP_GUIDE
        ),
        null
    );
    private final CoordinationDiagnosticsService coordinationDiagnosticsService;
    private final ClusterService clusterService;
    
    private static final String DETAILS_CURRENT_MASTER = "current_master";
    private static final String DETAILS_RECENT_MASTERS = "recent_masters";
    private static final String DETAILS_EXCEPTION_FETCHING_HISTORY = "exception_fetching_history";
    private static final String CLUSTER_FORMATION = "cluster_formation";
    private static final String CLUSTER_FORMATION_MESSAGE = "cluster_formation_message";
    
    public static final String INGEST_DISABLED_IMPACT_ID = "ingest_disabled";
    public static final String AUTOMATION_DISABLED_IMPACT_ID = "automation_disabled";
    public static final String BACKUP_DISABLED_IMPACT_ID = "backup_disabled";