OpenSearch Snap

[gabrielcocenza]

• use snap_daemon to not run service as root (not allowed by opensearch).
• install hook where place the config, data, logs folders and set permissions.
• overwrite jvm.options and opensearch.yml with right paths to logs and single-node discovery.
• system-files and mount-observe interfaces to have access to max_map_count and mount filesystem.
• security plugin using security.wrapper.

[gabrielcocenza]

Quick update on this PR:

The automatic connection for mount-observe interface was approved and as soon as the PR of snapd reaches the stable release, a new request will be necessary to include max_map_count into the system-observe interface (this will require changing the interface from system-files to system-observe in the snap code) and also a request for automatic connection to system-files to be able to create the override systemd file that is responsible for giving MEMLOCK, NPROC and NOFILE to the OpenSearch daemon.