This PR updates the LibSecret support to work correctly on KDE which uses a slightly different default collection.
With this PR the "default" alias is resolved and used by default. If no such collection is found, the collection `login` is used.
This was the intended logic before, but the alias was not resolved, so the code looked for a literal `default` collection and then fell back to `login`. On KDE systems this could cause issues by creating a new collection literally named `default` which would then fail to resolve.
With this update the libSecret works correctly on Plasma 6 (`kwalletd6`).
Support for Plasma 5 is not complete as the libsecret implementation there is different and deprecated. Here, installing Gnome Keyring is a workaround.
This fixes#6891
Kenneth Skovhede