Some decoupling from underscore => _.each pt2 => content overlays

[nathanwoulfe]

Prerequisites

• I have added steps to test this contribution in the description below

Description

This is an addition to #8475, splitting into multiple PRs to avoid giant merges. These changes remove underscore from the content overlay controllers (the ones used for the publish/save/unpublish overlays). Also fixes the sort order of variants displayed in the overlays (were previously in reverse alphabetical order, now in alpha order).

Change replace all underscore methods with native JS, and makes some general improvements (avoids iterating collections multiple times where possible, syntax fixes etc). Functionally, nothing has changed.

Testing requirement is to verify everything still works. Can save, publish, save+publish, unpublish, schedule with variant and invariant content. Changes are pretty safe and predictable as most relate to iterating the variants collection, which is always an array even if content is invariant.

There's a lot of duplication across these controllers, as there's a lot of common functionality (sorting, filtering) which would be really good to refactor. Hypothetically (😃) Typescript would make this more manageable as a variant object could become a variant class with its own methods, so duplicated controller functions would no longer be required to check properties as the variant would provide those values...

export class Variant {
  // lots of variant properties
  language: VariantLanguage;
  segment: VariantSegment;
  state: string;

  get isMandatory(): boolean {
    return this.language && this.language.isMandatory && this.segment;
  }
}

// elsewhere
const mandatoryVariants = vm.variants.filter(v => v.isMandatory());

Oh so lovely!