Split Content Model code (step 1)

[JiuqingSong]

To better consume Content Model and reduce initial bundle size, I'm splitting content model code into several packages, including

• roosterjs-content-model-types: Similar with roosterjs-editor-types, it provides type definitions for Content Model. This package will not generate any target js file
• roosterjs-content-model-dom: This package provides dom-to-model and model-to-dom conversion
• roosterjs-content-model-editor: This package provides ContentModelEditor and its core API, core plugins and other plugins, as well as format API. For now I have not split them into different packages like roosterjs-editor-core, roosterjs-editor-api, roosterjs-editor-plugins. But later we may do this change if need.
• roosterjs-content-model: Provide a general API createContentModelEditor(), also re-export functions from other packages

I also moved content model code to folder packages-content-model. After this change, the folder structure is like

• root
  • packages
    • roosterjs-editor-types
    • roosterjs-editor-dom
    • roosterjs-editor-core
    • roosterjs-editor-api
    • roosterjs-editor-plugins
    • roosterjs-color-utils
    • roosterjs-editor-types-compatible
    • roosterjs
  • packages-ui
    • roosterjs-react
  • packages-content-model
    • roosterjs-content-model-types
    • roosterjs-content-model-dom
    • roosterjs-content-model-editor
    • roosterjs-content-model

Also fixed test cases, and build scripts to adopt new file structures.

After this change, the bundle layout of content model is