Host bulk-actions stimulus controllers in separate action-models npm package

[pascallaliberte]

• Extract out the action-models-specific bulk actions Stimulus controllers into a separate action-models npm package
• Update the docs on how to install the action-models npm package once created

[pascallaliberte]

@andrewculver I've got this working in branches on the different repos (the npm package isn't created yet), but I'm not sure these Stimulus controllers should live in the private repo for the Pro-level plugin. The main reason: nobody can see the private repo, just the minified Stimulus controller javascript within the npm package.

If you're okay with bulk actions Stimulus controllers being only publicly visible via minified version inside the npm package, then I'll push the branches and setup the npm package.

Before all that, however, I recommend we merge the PRs about extracting select-all into its own controller. The new bulk-actions controllers are updated to expect a separate select-all controller.