Support control char reflection in mysql mariadb

Support control char reflection in mysql mariadb

Fixed issues regarding reflection of comments for :class:`_schema.Table`
and :class:`_schema.Column` objects, where the comments contained control
characters such as newlines. Additional testing support for these
characters as well as extended Unicode characters in table and column
comments (the latter of which aren't supported by MySQL/MariaDB) added to
testing overall.

Fixes: #9722
Change-Id: Id18bf758fdb6231eb705c61eeaf74bb9fa472601