This patch adds the new configuration option "debug" to enable debug
logging in mysqlrouter process, by default it will set the level to INFO
(mysqlrouter's default).
https://dev.mysql.com/doc/mysql-router/8.0/en/mysql-router-conf-options.html#option_mysqlrouter_level
Change-Id: If974a4525f3a6912125d11c7ca76c99c350c4f87
(cherry picked from commit d999571ae9)