Add key buffer size used and aria pagecache buffer size used

[pmachapman]

As I look at current report content, You have Open file limit used: n% (nn/nn). Consider adding:

• Key buffer size used: % ( key_blocks_used/((key_blocks_used)+(key_blocks_unused)) ) There are still plenty of people using MyISAM tables in production.

• Aria pagecache buffer size used: % ( aria_pagecache_blocks_used/((aria_pagecache_blocks_used)+(aria_pagecache_blocks_unused)) ) For those people beginning to adopt MariaDB and MySQL 8.0 in production.