MM-57193: Standardize the cache names (#26441)

We use the same name for hit/miss/invalidation metrics.

The downside is that now we have conflated a full cache purge
and a single cache key invalidation into a single label, but
the advantage is that it's easier to monitor the usage of a single
cache.

And moreover, duplicating the same string across multiple places
increases the chances of making a mistake. Centralizing the cache
name only at instantiation simplifies the code.

After this, we would be ready to use Redis.

https://mattermost.atlassian.net/browse/MM-57193

```release-note
NONE
```

server/channels/app/platform/service.go

@@ -275,6 +275,7 @@ func New(sc ServiceConfig, options ...Option) (*PlatformService, error) {
 
 	// Needed before loading license
 	ps.statusCache, err = ps.cacheProvider.NewCache(&cache.CacheOptions{
+		Name:           "Status",
 		Size:           model.StatusCacheSize,
 		Striped:        true,
 		StripedBuckets: maxInt(runtime.NumCPU()-1, 1),

server/channels/app/platform/status.go

@@ -65,12 +65,12 @@ func (ps *PlatformService) GetStatusesByIds(userIDs []string) (map[string]any, *
 		if err := ps.statusCache.Get(userID, &status); err == nil {
 			statusMap[userID] = status.Status
 			if metrics != nil {
-				metrics.IncrementMemCacheHitCounter("Status")
+				metrics.IncrementMemCacheHitCounter(ps.statusCache.Name())
 			}
 		} else {
 			missingUserIds = append(missingUserIds, userID)
 			if metrics != nil {
-				metrics.IncrementMemCacheMissCounter("Status")
+				metrics.IncrementMemCacheMissCounter(ps.statusCache.Name())
 			}
 		}
 	}
@@ -112,12 +112,12 @@ func (ps *PlatformService) GetUserStatusesByIds(userIDs []string) ([]*model.Stat
 		if err := ps.statusCache.Get(userID, &status); err == nil {
 			statusMap = append(statusMap, status)
 			if metrics != nil {
-				metrics.IncrementMemCacheHitCounter("Status")
+				metrics.IncrementMemCacheHitCounter(ps.statusCache.Name())
 			}
 		} else {
 			missingUserIds = append(missingUserIds, userID)
 			if metrics != nil {
-				metrics.IncrementMemCacheMissCounter("Status")
+				metrics.IncrementMemCacheMissCounter(ps.statusCache.Name())
 			}
 		}
 	}