Handle extensions enabled with LOAD

[ianstanton]

Some postgres extensions are enabled with LOAD or added to shared_preload_libraries instead of the traditional CREATE EXTENSION command (example: auto_explain). This PR adds logic to handle those types of extensions.

• Check if one of these extensions is installed by looking for <extension_name>.so in /var/lib/postgresql/data/tembo/15/lib
• Fetch trunk project metadata for a given extension
  • Example:

  [
    {
      "name": "auto_explain",
      "description": "The auto_explain module provides a means for logging execution plans of slow statements automatically, without having to run EXPLAIN by hand.",
      "documentation_link": "https://www.postgresql.org/docs/current/auto-explain.html",
      "repository_link": "https://github.com/postgres/postgres/tree/master/contrib/auto_explain",
      "version": "15.3.0",
      "postgres_versions": [
        15
      ],
      "extensions": [
        {
          "extension_name": "auto_explain",
          "version": "15.3.0",
          "trunk_project_name": "auto_explain",
          "dependencies_extension_names": null,
          "loadable_libraries": [
            {
              "library_name": "auto_explain",
              "requires_restart": true,
              "priority": 2147483647
            }
          ],
          "configurations": null,
          "control_file": {
            "absent": true,
            "content": null
          }
        }
      ],
      "downloads": [
        {
          "link": "https://cdb-plat-use1-prod-pgtrunkio.s3.amazonaws.com/extensions/auto_explain/auto_explain-pg15-15.3.0.tar.gz",
          "pg_version": 15,
          "platform": "linux/amd64",
          "sha256": "23eb345e8b5892c20f24a51d3c0de97198cde95a17c72426180f6d9b9ad8692b"
        }
      ]
    }
  ]
  

• If the extension has no control file && has a loadable library, skip traditional CREATE EXTENSION and add to shared_preload_libraries

[ChuckHend]

note this will need to be configurable soon as the coming changes for supporting pg14/16 come through.