Add XDG standard path auto-discovery for PVA TLS keychains#3782

kasemir merged 2 commits intoControlSystemStudio:masterControlSystemStudio/phoebus:masterfrom

george-mcintyre:feat/pva-xdg-keychain-discoverygeorge-mcintyre/phoebus:feat/pva-xdg-keychain-discoveryCopy head branch name to clipboard