This adds the final HPKE version string.

This removes the draft version markers from the implementation and stops
tracking the draft version with the exported syntax.

I've added the script that I used to convert the JSON test vectors from the
specification; that should allow us to pick up new tests relatively easily,
especially if we need to add new algorithms.

This change breaks several ECH test cases.  As fixing those tests is
extraordinarily fiddly, I'm going to defer making those changes until we need to
update ECH.  As we can't land this code until ECH is updated to depend on the
final HPKE and until we have coordinated with servers on when the ECH update can
be deployed, it should be OK to defer.

In short, don't land this without the matching ECH changes.

Differential Revision: https://phabricator.services.mozilla.com/D105256

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extra : rebase_source : b0717403cf5136efc14f85499182763aa551efc3

The main changes here are:

* an update to HPKE -08
* a move to the single-byte configuration ID
* reordering of ECHConfig

The addition of the explicit configuration ID means that the API for
constructing ECHConfig(List) needs to change.  That means a name change,
unfortunately.  I took the opportunity to make further changes to the arguments.

Differential Revision: https://phabricator.services.mozilla.com/D108392

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extra : rebase_source : e66ae86be746afbadc6c444d0debcc5aaabd2eb5

Differential Revision: https://phabricator.services.mozilla.com/D108734

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extra : rebase_source : ffa43f8cd1f341d56e8782f81a2aa24243533614