### 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
return NAME;
    }
    @Override
    public HealthIndicatorResult calculate(boolean explain, HealthInfo healthInfo) {
        CoordinationDiagnosticsService.CoordinationDiagnosticsResult coordinationDiagnosticsResult = coordinationDiagnosticsService
            .diagnoseMasterStability(explain);
        return getHealthIndicatorResult(coordinationDiagnosticsResult, explain);
    }
    /**
     * Transforms a CoordinationDiagnosticsService.CoordinationDiagnosticsResult into a HealthIndicatorResult.
     * @param coordinationDiagnosticsResult The CoordinationDiagnosticsResult from the CoordinationDiagnosticsService to be transformed
     * @param explain If false, the details and user actions returned will be empty
     * @return The HealthIndicatorResult
     */
    
    HealthIndicatorResult getHealthIndicatorResult(
        CoordinationDiagnosticsService.CoordinationDiagnosticsResult coordinationDiagnosticsResult,
        boolean explain
    ) {
        HealthStatus status = HealthStatus.fromCoordinationDiagnosticsStatus(coordinationDiagnosticsResult.status());
        HealthIndicatorDetails details = getDetails(coordinationDiagnosticsResult.details(), explain);
        Collection<HealthIndicatorImpact> impacts = status.indicatesHealthProblem() ? UNSTABLE_MASTER_IMPACTS : List.of();
        List<Diagnosis> diagnosis = status.indicatesHealthProblem() ? getContactSupportUserActions(explain) : List.of();
        return createIndicator(status, coordinationDiagnosticsResult.summary(), details, impacts, diagnosis);
    }
    /**
     * Returns a HealthIndicatorDetails populated with information from the coordinationDiagnosticsDetails. If explain is false,
     * HealthIndicatorDetails.EMPTY will be returned. Otherwise the xContent of the returned HealthIndicatorDetails will potentially
     * include some of "current_master", "recent_masters", and "exception_fetching_history" top-level objects. The "current_master" field
     * will have "node_id" and "name" fields. The "recent_masters" field will be an array of objects, each containing "node_id" and