Upgrade `MaterialUI` to v5

[rubenthoms]

In order to (hopefully) get rid of some issues with conflicting class names in wcc and wsc and to also make use of the newest functionalities, we should upgrade MaterialUI in wcc to v5. If the upgrading goes well in wcc, we can also consider to upgrade it in wsc.

[anders-kiaer]

In offline discussions we decided that we can simply ✂️ delete wcc.ColorScales now, and thereby probably being able to push #244 to the finish line 🏁.