Clean up EML211EditorView to address issues with submitting datasets

[robyngit]

The EML211EditorView is currently difficult to maintain and extend due to its size and complexity. We need to make it more modular and readable in order to address issues users are encountering with submitting datasets.

During the clean-up, we will:

• Fix all linting errors (includes switching to modern JS syntax). Add missing JSdoc comments.
• Refactor long methods into smaller & reusable functions, especially the render method. Maybe split the view into smaller sub-views.
• Use async/await for to replace nested callbacks
• Improve error handling and prevent silent failures
• Extract repeated code into reusable functions
• Cleanup of event listeners by using stopListening to prevent memory leaks and zombie event handlers
• Move model logic out of the view and into models to leverage Backbone's built-in methods like defaults and validate
• Simplify conditional assignments and avoid deep nesting

[robyngit]

There are a series of steps taken in the EML211EditorView to ensure that the user has the correct permissions to edit the metadata and resource map and metadata:

1. Make sure the user is signed in
2. Fetch the metadata
3. Use the metadata to identify and then fetch the resource map
4. Make sure the user has write permission on the metadata
5. Make sure the user has write permission on the resource map

These steps add quite a bit of complexity to the view and really fit better in a model. The DataPackage model is a natural place to move this logic to, and would simplify the process. There may be other views that could reuse these methods as well. Before moving them, we should first finish the DataPackage clean-up. So this issue is on the back-burner until issue #2567 is completed.