Consolidate functionality across core into single module (vdom.ts)

[agubler]

Type: feature

The following has been addressed in the PR:

• There is a related issue
• All code has been formatted with prettier as per the readme code style guidelines
• Unit or Functional tests are included in the PR

Description:

After merging widget-core with core, this change colocates all the functionality required to build and use Dojo widgets into a single module, vdom.ts. The driver for this is not having a sane place to put the new create factory for functional widgets and middleware. Also to reduce the minumum number of modules a user needs to import for Dojo.

Before

import { renderer, create } from '@dojo/framework/core/vdom';
import { v, w } from '@dojo/framework/core/d';
import { tsx } from '@dojo/framework/core/tsx';

After

import { renderer, create, v, w, tsx } from '@dojo/framework/core/vdom';

Note: This will require some additional work for the @dojo/cli-upgrade-app to seamlessly migrate user codebases to the new imports.