[DOM-49106] Emit image size as part of build

[ddl-rliu]

Problem

When an image is built, we do not track the size of the image

Solution

Track the size and return it as compressedImageSizeBytes, part of the Annotations field in the BuildSucceeded response message at the end of a build.

We do this in Hephaestus, rather than Nucleus. This is because Nucleus does not talk with the registry; rather, it sets up the registry configs/auth and defers the responsibility to Hephaestus (which then defers it to buildkit). This PR queries the registry in order to track the size, and Hephaestus seems preferable since it is "closer" to buildkit.

https://dominodatalab.atlassian.net/browse/DOM-49106

1. This PR does not handle multi-arch images. This (and the other below item) is tracked in a followup ticket https://dominodatalab.atlassian.net/browse/DOM-53850
2. This PR only handles Hephaestus images.