Add Intl.DisplayNames types

[TimvdLippe]

The TC39 proposal (https://github.com/tc39/proposal-intl-displaynames)
reached stage 4 in September 2020.

Fixes #41338

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• There is an associated issue in the Backlog milestone (required)
• Code is up-to-date with the master branch
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• There are new or updated unit tests validating the change

[sandersn]

@DanielRosenwasser you previously commented on #40786 saying that Intl is not part of the main TC39 spec, so in #40709 we added a property to NumberFormatOptions to ES5 instead of ES2020. Where does Intl.DisplayNames fall? How do I tell so I can review these PRs myself?

[TimvdLippe]

@DanielRosenwasser Friendly ping for the above question 😄

[orta]

In the meantime, a strange request but I'd prefer it to have less jsdoc information. We ship all of these dts files to consumers on npm and web which means we need to try keep the filesize somewhat reasonable and the dts files account for the many mbs which people have to download before anything can happen.

Any chance you can drop the @param info to just oneliners?

[TimvdLippe]

@orta I would absolutely love to, as it was an absolute pain to get all the formatting correct. However, a lot of the other types do have the JSDoc there. Therefore, does it make sense to first drop all of these and then we update existing PRs to also drop the information?

[TimvdLippe]

@DanielRosenwasser We would like to remove the local patch we have in DevTools. Could you please provide a status update for what we should do with shipping these internationalization type APIs?

[orta]

Thanks for the PR, I've merged these changes in with a big overhaul of all Intl APIs for 4.5 - #45647