Add Intl.NumberFormat Unified API support in Safari 14.1

[chicoxyzzy]

Intl.NumberFormat Unified API is Supported in Safari 14.1.

Examples for testing could be found here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/NumberFormat

Safari 14.1 is available for Apple Developers program members

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[ddbeck]

Hi @chicoxyzzy and thanks for opening this PR. Unfortunately, we're not yet tracking the next release of Safari (this is the cause of the CI failure). It's my understanding that there's some fuzziness around what features will graduate to a general release, so we're holding off for now. In the meantime, I'm going to mark this as blocked. Thank you!

[lukewarlow]

This was addressed by #10129, which has been merged.

[chicoxyzzy]

I think this PR could be closed as #10129 has been merged