Naive implementation of using mimeapps.list "Default Applications" to load default app associated with scheme
for instance x-scheme-handler/mailto for mail clients.
This should be handled by kbuildsyscoca.
This is an effort to replace usage of KEmailSettings / emaildefaults
Specs:
https://specifications.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-latest.html
https://specifications.freedesktop.org/mime-apps-spec/mime-apps-spec-latest.html