Updates to Dream instrument view

[nvaytet]

We simplify and improve the performance of the Dream instrument view, and replace the single-valued slider with a range slider for the tof dimension.

Instead of having one node per detector bank that points to the scatter3d figure, we merge all banks from the data group into a single data array.
This vastly improves performance when moving clipping planes and interacting with the time-of-flight slider.

We had to remove the checkboxes that would hide/show individual banks, but it is believed that they were not very useful in practice (see #101 (comment)).
If we want to select a subset of banks, we filter from the data group that is sent to the view before creating it.
Users most likely will want to see all banks most of the time. Dynamically toggling is probably unnecessary.

Fixes #101

This would also fix #102 if scipp/plopp#479 is added to Plopp.

[nvaytet]

@celinedurniak please take a look and see what you think.

[celinedurniak]

Hi,
I tested the new instrument view using the notebook from the online documentation (https://scipp.github.io/essdiffraction/user-guide/dream/dream-instrument-view.html).

From your comments at #101 (comment)

• I found the check boxes useful in order to display, for example, the mantle or the SANS or HR detector banks without having to deal with the endcaps.
  But as you mentioned, we can always code the display of a few selected banks instead of having check boxes.

• For the slider, it would be nice to be able to select between a range slider and a standard one because if the range is too small, it is difficult to move.

[nvaytet]

For the slider, it would be nice to be able to select between a range slider and a standard one because if the range is too small, it is difficult to move.

I added some toggle buttons that allow to switch between range slider and single slice slider.