* Add Amazon Linux 2 as a supported OS.
* Dynamically select the package manager for Amazon and Oracle Linux.
* Prepare for supporting PostgreSQL 18. Specifically, the Docker image
seems to have moved the data directory, so get that dynamically.
* Add a mode to test all metric queries
* Add a script to run query tests against different versions of
PostgeSQL
* Add Docker elements for query testing
* Switch to using a --config flag when specifying the config file
* Fix some metric queries
* Allow the agent address to be configured
* Allow the sslmode connection parameter to be configured
