Replace core/internal.backbone library

Problem/Motivation

Follow-up from 🐛 Use core/internal.backbone lib Needs work .

Depending on an "internal" library will result in problems down the road if they decide to remove it.

#3258931: Deprecate backbone and tag it internal →
#3145958: [META] Re-evaluate use of Backbone.js in core →
#3204015: Replace Toolbar BackboneJS usage with VanillaJS equivalent →

Proposed resolution

Replace the need for using backbone. Follow what is being done in #3204015: Replace Toolbar BackboneJS usage with VanillaJS equivalent →