Hash key for plugin store table and limit plugin ID length (#7915)

* Hash plugin store keys and update column limits

* Limit plugin ID length on install

* Add note to manifest id and allow zero length keys

store/sqlstore/plugin_store.go

@@ -21,8 +21,8 @@ func NewSqlPluginStore(sqlStore SqlStore) store.PluginStore {
 
 	for _, db := range sqlStore.GetAllConns() {
 		table := db.AddTableWithName(model.PluginKeyValue{}, "PluginKeyValueStore").SetKeys(false, "PluginId", "Key")
-		table.ColMap("PluginId").SetMaxSize(100)
-		table.ColMap("Key").SetMaxSize(100)
+		table.ColMap("PluginId").SetMaxSize(200)
+		table.ColMap("Key").SetMaxSize(50)
 		table.ColMap("Value").SetMaxSize(8192)
 	}