This patch implements the part of T12441 that was virtually universally agreed-to:
switching out the regular Task Manager for an Icons-Only Task Manager and pinning
some apps by default. The panel is also thickened to to 46px (with the default font).
The panel remains in its current position pending further discussion about whether
or not we want to move it to the left edge.
Ideally I'd like for this patch to used for discussions about the implementation, not the
general concept, so if you have concerns about that, please put them in T12441.
Also note that https://bugs.kde.org/show_bug.cgi?id=418483 currently breaks the IOTM
icons from keeping their position, which would definitely need to be fixed before this
lands.