[mobile/wifi] Move network en/disable into main action

Summary: The current switch at the top is both not very visually appealing and violates the Kirigami principle of putting relevant controls on the bottom where they are easily reachable

Test Plan:
Before:
{F6949803}

After:
{F6949796}

Reviewers: #vdg, #plasma, jgrulich, mkacej

Reviewed By: jgrulich

Subscribers: ngraham, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D22179