MM-37034: Bump the MySQL min version to 5.7 (#17919)

* MM-37034: Bump the MySQL min version to 5.7

https://mattermost.atlassian.net/browse/MM-37034

```release-note
Minimum required MySQL version is now 5.7
```

* fix shadow warnings

```release-note
NONE
```

* Bumped to 5.7.12

```release-note
NONE
```

* update comment

```release-note
NONE
```

* refactor

```release-note
NONE
```

* fix lint error

```release-note
NONE
```

* fix2

```release-note
NONE
```

* add tests

```release-note
NONE
```

* simplify

```release-note
NONE
```

build/docker-compose.common.yml

@@ -1,7 +1,7 @@
 version: '2.4'
 services:
   mysql:
-    image: "mysql:5.6"
+    image: "mysql:5.7.12"
     restart: always
     networks:
       - mm-test
@@ -19,7 +19,7 @@ services:
     volumes:
       - ./docker/mysql.conf.d/source.cnf:/etc/mysql/conf.d/mysql.cnf
   mysql-read-replica:
-    image: "mysql:5.7"
+    image: "mysql:5.7.12"
     restart: always
     networks:
       - mm-test