feat(Import Step): Move to Create New Step Menu

[hirokiterashima]

Notes

• @breity please feel free to style and re-word elements as you see fit
  • For example, should the "Create New Step" button be "Add New Step" in the project-authoring view?

Changes

• Move "Import Step" option to "Create New Step" menu (before: "Import Step" was a top-level option in the project-authoring view). This will remove the top-level button in project-authoring view by 1, and make the import step workflow similar to import component flow.

Test

• "Import Step" option is available through "Add New Step" menu
• "Import Step" workflow works as before, including back/cancel buttons

Closes #1444

[breity]

Functionality works well. 👍

I made a couple changes:

• Removed unused description field from NewNodeTemplate.
• Removed unnecessary aria-label attributes from buttons that have label text.

One request: For consistency, could we add a back button to the "Choose a unit from which to import step(s)" stage in the import sequence?

I think changing "Create New Step" to "Add New Step" could make sense. If we do, we should also change "Create New Lesson" to "Add New Lesson" to be consistent.

[hirokiterashima]

Good suggestions. I made the changes. PTAL.

[breity]

LGTM 👍