Summary:
Combines settings of SNI icons and plasmoids in one list. Ability to disable whole section is removed.

Initial idea was proposed by Nicolas Fella (D22176).

BUG: 360307
FIXED-IN: 5.18.0

{F7880936}

Test Plan:
1. Disable/enable plasmoids
2. Set Shown/Hidden for plasmoid
3. Set shortcut for plasmoid
4. Previously hidden categories are shown
5. Show all icons and revert
6. Set Auto/Shown/Hidden for SNI icons

Reviewers: #plasma_workspaces, #plasma, davidedmundson, broulik, ngraham, mart

Reviewed By: #plasma_workspaces, #plasma, ngraham, mart

Subscribers: ahiemstra, mart, meven, nicolasfella, plasma-devel, ngraham

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D26586