Rewrite servicemenu helper utility in C++

Summary:
     - Also support MIME type "application/x-compressed-tar".
     - Update tests in Ruby, remove SimpleCov.

BUG: 399229

Test Plan: Ruby tests passed

Reviewers: sitter, elvisangelaccio, ngraham

Reviewed By: elvisangelaccio

Subscribers: cfeck, kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D21878