Build Tooling: Avoid .default on browser global assignments

[aduth]

Related: #11825 (comment)

This pull request seeks to correct wrongly-assigned .default values on browser-assigned globals. In master you will observe both a wp.tokenList.default and a wp.coreData.default.

This was discovered with the following console code:

Object.entries( wp ).filter( ( [ key, value ] ) => value.default )

Open question: These are technically breaking changes, though very much of the "this was obviously always broken" sort. We don't use core-data's default export anywhere, nor should anyone. Should we have any deprecation process here?

Testing instructions:

Verify that wp.tokenList is the default exported function.

Verify there is no wp.coreData.

Follow-up tasks:

As noted at #11825 (comment) and similarly considered in Slack (link requires registration), we should consider correcting the naming of tokenList and escapeHtml.

[gziolo]

I'm fine with the changes proposed. I don't think that someone would use wp.tokenList.default in their code. It's a very low-level utility object. We should fix it now rather than support indefinitely for backward compatibility.

[youknowriad]

We should not forget to update this in Core's webpack too :)