Prepare and publish Open MCT e2e framework as a separate package

[ozyx]

Summary

In a previous PR, we prepared our e2e framework to be published as a separate package. This ticket captures the work to bring it over the finish line, culminating in the publishing of @openmct/e2e, our e2e testing framework, so that other projects that consume Open MCT may use it for testing purposes.

Included:

• Rename openmct-e2e to @openmct/e2e to make use of the @openmct npm namespace
• Update the directory structure to use the packages/* pattern for npm workspaces
  • This allows us to easily add other subpackages in the future, and potentially integrate with a monorepo management tool should we decide we need one
• Ensure that all package.json scripts continue to function and all tests pass with the new structure
• Ensure that code coverage continues to be correctly generated and analyzed with the new structure
• Ensure that a consuming project (such as openmct-yamcs) can install and use @openmct/e2e in its tests
• Publish a -next (alpha) version of @openmct/e2e for testing purposes