[kprocessrunner] Escape hyphen characters in scope names

Summary:
Desktop names can be from the set "ASCII letters, digits, dash (U+002D
HYPHEN-MINUS) and underscore (U+005F LOW LINE). "

Hyphen is a special character in systemd units indicating a logical tree
level. We would process drop-ins incorrectly, Specification says they should be escaped.

Test Plan:
Ran elf-dissector
systemdcg-ls showed
org.kde.elf\x2ddissector-0dc652e69f5d4557873db10d03517b41.scope

Reviewers: apol

Reviewed By: apol

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D28510