Summary:
Restrict to process with `X-KDE-DBUS-Restricted-Interfaces=org.kde.kwin.Screenshot` in their corresponding Service file,
to take screenshots.
Such a program can now take immediate screenshots.
Adds a utility file to group KService related logic.
Needed for D29408
Reviewers: #kwin, apol, davidedmundson, bport, zzag
Reviewed By: #kwin, davidedmundson
Subscribers: ngraham, kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D29407
e3df2e15a6