Fix DateTimeTz type compatibility on SQL Anywhere versions < 12

SQL Anywhere versions < 12 do not support a native date time with timezone type. Therefore the fallback strategy is to use the normal date time type. However the format of the date time tz type declaration has to correspond to the normal date time type declaration, too then.

`getDateTimeTzTypeDeclarationSQL()` -> `getDateTimeTypeDeclarationSQL()`
`getDateTimeTzFormatString()` -> `getDateTimeFormatString()`

I thought about changing that in the `AbstractPlatform` but I am not sure if that might break assumptions in userland code and therefore BC. So I left the implementation SQL Anywhere specific.