Scrollbar with new theme

[Cuervino]

Component:

Scrollbar

Why this is needed: For matching the latest theme; for having consistency

What should be done: Update the colors of the scrollbar and its states

Implementation proposal (strongly recommended):

https://www.figma.com/file/qrsV3Oh7XZHDhZfdk5jZWI/core-ui?node-id=27%3A20