[WIP] UI intensity slider for the KDE rendering API

[JoaoDell]

Hello everyone, this is a draft PR to implement a UI intensity slider for the KDE rendering API. It is a simple slider that controls the intensity of the bandwidths:

Currently, it is based on the old version of the API and shall be updated to match the current one, but I am already going to open this so it is properly registered. One important thing to say is that, the way it is now, it is for some reason I still don't know, crashing. When I work on it again I am going to investigate it and probably open an issue, so expect updates.

[codecov]

Codecov Report

Merging #849 (1c4c52c) into master (e0741be) will decrease coverage by 1.20%.
The diff coverage is 0.65%.

@@            Coverage Diff             @@
##           master     #849      +/-   ##
==========================================
- Coverage   84.49%   83.30%   -1.20%     
==========================================
  Files          44       45       +1     
  Lines       10454    10605     +151     
  Branches     1411     1420       +9     
==========================================
+ Hits         8833     8834       +1     
- Misses       1252     1402     +150     
  Partials      369      369              

Files Changed	Coverage Δ
fury/actors/effect_manager.py	0.00% <0.00%> (ø)
fury/shaders/__init__.py	100.00% <ø> (ø)
fury/window.py	77.77% <0.00%> (-0.30%)	⬇️
fury/shaders/base.py	89.21% <33.33%> (-1.70%)	⬇️