Change mysql library to mysql2 as it is more maintained and support latest mysql authention (#862)

* Use mysql2 lib

* fix pool on acquire event cause MaxListenersExceededWarning (#854)

before: every query need to register pool on acquire event to specify queryFormat based on payload type
will cause MaxListenersExceededWarning

after:
from https://www.npmjs.com/package/mysql#pooling-connections

pool.query is a shortcut for pool.getConnection() -> connection.query() -> connection.release()

so use pool.getConnection and then
set queryFormat before query method be called

Co-authored-by: Dave Conway-Jones <dceejay@users.noreply.github.com>

* fix mysql require

* Add decimalNumbers flag true to mysql beta

* mysql remove old Timeout option, clarify timezone options

* add mysqlConnectionLimit settings option.

Co-authored-by: saknarak <saknarak@gmail.com>

storage/mysql/locales/en-US/68-mysql.json

@@ -19,6 +19,7 @@
             "notstring": "the query is not defined as a string",
             "notconnected": "Database not connected",
             "notconfigured": "MySQL database not configured"
-        }
+        },
+        "tip": "Tip: The timezone should be specified as ±hh:mm or leave blank for 'local'."
     }
 }