add ng-select for templatable select options

[rigelk]

Having a slightly more customizable select component is required here to display both the label of an option and its description. ng-select component, like most select components around, features lazy-loading of remote data - which could prove useful for listing channels in the video-edit view in the future.

In this PR I focus on the upload/edit view, but other select usages could use option templates elsewhere.

fixes #3015

[rigelk]

@Chocobozzz I didn't check bundle size, because I think this component could replace ngx-tag as well and save on its size: https://ng-select.github.io/ng-select/#/tags

Considered this, I didn't try to target the video-update module only.

[Chocobozzz]

😍

[Chocobozzz]

Would be happy if you could remove ngx-tag

[rigelk]

@Chocobozzz I made progress, but I also have a strange error that might be due to my modifications of the video-edit view:

DEBUGGED:

• it is due to errors that block further rendering:
  • a missing input that I forgot while extending the base NgSelectComponent.
  • bindValue that cannot find the nested attribute (key) when reseting.

[rigelk]

@Chocobozzz I replaced ngx-chips as intended, and while my select-tags component behaves well in forms (in the video-edit view), I can't seem to make it work in the search-filter component, where there is no form and two-way data binding doesn't seem to work with it. I could always replace the component with the bare ng-select component, but it kinda defeats the factorization.

Aside from this, it is mostly on par with previous functionality. Slight differences: channel avatars, instance languages on top of language list and grouped as such.