[Notes] Port to QQC2 and use GridView KCM components for the color chooser

Summary:
Additional changes:
- Use standard import names

Thanks to @gb_2 for providing the skeleton of this patch

Test Plan:
Everything works and color value is saved and loaded properly
{F6824154}

Reviewers: #vdg, #plasma, GB_2, ndavis, mart

Reviewed By: #vdg, #plasma, ndavis, mart

Subscribers: mart, ndavis, GB_2, plasma-devel

Tags: #plasma

Maniphest Tasks: T10586

Differential Revision: https://phabricator.kde.org/D21221