Enable three more plugins by default

Summary:

• Cuttlefish Icon Chooser
• File Browser (not on Windows because it is unstable there)
• Terminal Tool View (not on Windows because it does not work there)

Test Plan:
Remove ~/.config and started Kate. All new plugins are enabled by default.

I also tested with a plugin that does exist (to simulate users that don't have the plasma5-sdk with the cuttlefish plugin installed). There was no error.

Reviewers: Kate, dhaumann

Reviewed By: Kate, dhaumann

Subscribers: kossebau, dhaumann, sars, ngraham, kwrite-devel

Tags: Kate

Differential Revision: https://phabricator.kde.org/D16641