[Super Cache] Allow site owner to disable some warnings

Allow the site owner to disable the read-write checks on the wp-cache-config.php config file.

Allow them to disable the wp-cron checks too, as it may be handled by an external cron system.

This should be done by setting constants in wp-config.php as these can negatively impact a site.

ref: https://wordpress.org/support/topic/disable-admin-warnings/

Start by locating the read-write checks for wp-cache-config.php and the wp-cron checks, then review how wp-config.php constants are read. Define the constants and their expected disabled behavior from the issue requirements, and verify that each corresponding admin warning is suppressed without affecting other checks.

Written by the indexing model from the issue text.