Add Canvas workpads to Saved Object Management

[kibanamachine]

Original comment by @alexfrancoeur:

I don't know where to put this for now, but I'm assuming it will carry over when we merge into the Kibana repo. End users should be able to export all or select workpads through the saved object management UI. This way with a single export, they can carry over their entire environment. This could be more common with Spaces introduced as well.

[rayafratkina]

cc @nreese @alexfrancoeur @rashidkpc
We should make sure we are using saved object apis for import/export for GA.

[ambigus9]

Any advance to implement this feature?

[rashidkpc]

wooooooooooooo