[Applet] Display device name when there is than one device

Summary:
Display both device name and port if there is more than one device.
Applies separately for playback and recording devices.

BUG: 417079

Reviewers: #plasma, #vdg, drosca, ngraham

Reviewed By: #vdg, ngraham

Subscribers: cgiboudeaux, broulik, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D27138