Widgets update

[anthoninlize]

Update widgets to pure external UI framework components.
Re. https://developers.arcgis.com/javascript/latest/custom-widget/

"Deprecation notice - as of 4.27, it is no longer recommended to subclass or extend /esri/widgets/Widget as the basis for building a fully custom widget. This pattern creates dependencies on SDK internals and can result in frequent and undocumented breaking changes. The guide content below follows the legacy patterns, and should only be used for maintaining existing widgets."

"When building custom widgets, it is recommended to use the @arcgis/core ES modules with the front-end JavaScript framework of your choice. Frameworks such as React, Angular, Vue.js and others are not required, however they offer the greatest amount of scalability. You can create multiple widgets that are loosely coupled with the SDK, and that adhere to the framework's well known UI/UX patterns and component life-cycle. Refer to the jsapi-custom-widget sample to see how to create your own custom widget."