MM-62079: Using a cache prefix to isolate cache keys for each test (#30261)

```release-note
A new config setting CacheSettings.RedisCachePrefix has been added which can be used to add a prefix to all Redis cache keys.
```

server/channels/api4/apitestlib.go

@@ -113,6 +113,7 @@ func setupTestHelper(dbStore store.Store, searchEngine *searchengine.Broker, ent
 		*memoryConfig.CacheSettings.RedisAddress = redisHost + ":6379"
 		*memoryConfig.CacheSettings.DisableClientCache = true
 		*memoryConfig.CacheSettings.RedisDB = 0
+		*memoryConfig.CacheSettings.RedisCachePrefix = model.NewId()
 		options = append(options, app.ForceEnableRedis())
 	}
 	if updateConfig != nil {

server/channels/api4/post_test.go

@@ -131,7 +131,6 @@ func TestCreatePost(t *testing.T) {
 	})
 
 	t.Run("Create posts without the USE_CHANNEL_MENTIONS Permission - returns ephemeral message with mentions and no ephemeral message without mentions", func(t *testing.T) {
-		t.Skip("MM-62764")
 		wsClient := th.CreateConnectedWebSocketClient(t)
 
 		defaultPerms := th.SaveDefaultRolePermissions()
@@ -188,7 +187,6 @@ func TestCreatePost(t *testing.T) {
 				}
 			case <-timeout:
 				require.Fail(t, fmt.Sprintf("Got %d ephemeral messages, expected: %d", gotEvents, expectedEvents))
-				break
 			}
 		}
 	})