Fix slider in image contrast editor on python >=3.10

[ericpre]

On python 3.10, the slider of the image contrast editor are broken:

import hyperspy.api as hs
import numpy as np

hs.preferences.GUIs.enable_traitsui_gui = True
hs.preferences.GUIs.enable_ipywidgets_gui = False

s = hs.signals.Signal2D(np.random.random(10000).reshape((100, 100)))
s.plot()

Press on h key to open the image contrast editor and the percentile slider are missing.

The error is:

  File "C:\Users\M0041User\mambaforge\lib\site-packages\traitsui\qt4\extra\range_slider.py", line 81, in paintEvent
    opt.sliderPosition = value
TypeError: 'float' object cannot be interpreted as an integer
Traceback (most recent call last):
  File "C:\Users\M0041User\mambaforge\lib\site-packages\traitsui\qt4\extra\range_slider.py", line 81, in paintEvent
    opt.sliderPosition = value
TypeError: 'float' object cannot be interpreted as an integer
Traceback (most recent call last):
  File "C:\Users\M0041User\mambaforge\lib\site-packages\traitsui\qt4\extra\range_slider.py", line 81, in paintEvent
    opt.sliderPosition = value
TypeError: 'float' object cannot be interpreted as an integer
Traceback (most recent call last):
  File "C:\Users\M0041User\mambaforge\lib\site-packages\traitsui\qt4\extra\range_slider.py", line 81, in paintEvent
    opt.sliderPosition = value
TypeError: 'float' object cannot be interpreted as an integer
Traceback (most recent call last):
  File "C:\Users\M0041User\mambaforge\lib\site-packages\traitsui\qt4\extra\range_slider.py", line 81, in paintEvent
    opt.sliderPosition = value
TypeError: 'float' object cannot be interpreted as an integer

xref enthought/traitsui#2048 for a fix in traitsui.

Needs hyperspy/hyperspy#3368

[codecov]

Codecov Report

Attention: Patch coverage is 41.22137% with 154 lines in your changes are missing coverage. Please review.

Project coverage is 44.83%. Comparing base (7b70620) to head (96fae29).

Files	Patch %	Lines
hyperspy_gui_traitsui/_external/range_slider.py	18.69%	99 Missing and 1 partial ⚠️
hyperspy_gui_traitsui/_external/bounds_editor.py	60.86%	50 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #76      +/-   ##
==========================================
- Coverage   47.34%   44.83%   -2.51%     
==========================================
  Files          10       12       +2     
  Lines         452      707     +255     
  Branches       72      104      +32     
==========================================
+ Hits          214      317     +103     
- Misses        230      378     +148     
- Partials        8       12       +4     

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[ericpre]

Merging this PR to release, to prepare to be able to release soon after hyperspy 2.1 is released.