Replace wp globals with module equivalents

[aduth]

Previously: #716, #736, #737, #739

This pull request expands upon the restructuring outlined in #716, replacing wp. global calls with their "WordPress modules" equivalents. It should be the final step in this process.

Testing instructions:

Ensure the build completes, tests pass, and editor initializes and appears without regressions. Specifically observe that no errors are logged to the console, blocks appear as registered with localized (likely English) labels intact.

[aduth]

Rebased to resolve conflicts, include new additions, and also remove wp as a whitelisted global so access attempts in code throw lint errors (249ccfc).

I discovered in the process that we may also want to change our React pragma from wp.element.createElement to createElement. This has the downside of meaning we'd now need to import { createElement } from 'element'; in every single file using JSX. I'm going to reserve this for a future pull request.

[youknowriad]

import { createElement } from 'element'; in every single file using JSX

@aduth I think this is good thing, it makes things more explicit.

I think you should rebase and merge this branch right after, because you'll always have conflicts :)

[nylen]

Let's just change this to import React from 'react' already.

Edit: though I agree that should be a future PR.

[nylen]

@aduth I think we should proceed with this, though arguably it would be easier to just start over. I can help if you like. Do you have concerns with the approach here?

[aduth]

@nylen

Yes, we should probably do this, and it's probably easier to start over (essentially a find-replace on wp. + import).

One main concern is other wp globals like wp.api.models.Post. How do we handle these?

[nylen]

Good question... also seems related to #941.

[aduth]

Superseded by #1332