Add implementation of unified vault format (UVF).

[dkocher]

Resolves #16642.

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 3 committers have signed the CLA.

✅ dkocher
✅ ylangisc
❌ chenkins
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 3 committers have signed the CLA.

✅ dkocher
✅ ylangisc
❌ chenkins
_{You have signed the CLA already but the status is still pending? Let us recheck it.}