Update .ebextensions (add Cloudwatch agent & AWS Inspector) (#14718)

* Update .ebextensions to send memory usage to Cloudwatch and also install inspector agent to actively monitor threats. Added full Cloudwatch agent with metrics config, simplified config file. Fix #9021

* Adding a few items to documentation

* Apply suggestions from code review

Co-authored-by: Jeff Bruemmer <jeff@metabase.com>

* Add a few more changes to finish this PR

Co-authored-by: Jeff Bruemmer <jeff@metabase.com>