Respect the XDG Base Directory Specification

Running the `pack download` command in codeql writes results to a $HOME/.codeql directory.

It would be nice if codeql conformed to the freedesktop guidelines about where to write user data, as specified here: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

That would make it easier to know where the programs data is located, and not clutter my home directory.

Start with the `pack download` command and compare its current `$HOME/.codeql` location with the linked freedesktop XDG Base Directory Specification. No source file or test is named in the issue, so locate the path-handling entry point first; done means user data follows the applicable XDG location without cluttering the home directory.

Vom Indexierungsmodell aus dem Issue-Text verfasst.