Dashboard: support importing devfiles

[bryantson]

Is your enhancement related to a problem? Please describe.

Currently, Devfile can be either modified through Devfile registry or dynamically through the browser editor by going into the Workspace setting. However, due to different browser issue and autosaving feature, Devfile is difficult to change and the autosaving feature does not help

Describe the solution you'd like

1. Provide the button to import the Devfile from a local computer.
2. Replace the autosaving feature with the button to save, delete, etc.

Describe alternatives you've considered

Additional context

[l0rd]

@bryantson thanks for raising it. I think we should separate the issues: allow devfile import is one issue and disabling the autosaving is a distinct one.

There is no doubt that supporting a devfile import would be useful.

I have some doubts about disabling the autosaving. IMHO if there are issues with autosaving we should fix them instead of disabling it. Please open a separate issue for that.

[amisevsk]

For autosave, we already have #13982 -- it can be an enormous pain.

[azatsarynnyy]

closing it as both features are already implemented