Reland "Enable disk image based import/export for termina guests"

This reverts commit 4bb9461462e86cb13961fd34e338ed9b98361aa7.

Reland fixes long <-> int64_t conversion to ensure portability.

Bug: b:345312503
Change-Id: I08e4d9a6a9404fe9a81a15ff07e80a750f1f1319
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6842702
Reviewed-by: Hamda Mare <hmare@google.com>
Reviewed-by: Timothy Loh <timloh@chromium.org>
Commit-Queue: maciek swiech <drmasquatch@google.com>
Reviewed-by: Chad Duffin <chadduffin@chromium.org>
Reviewed-by: Josh Simmons <simmonsjosh@google.com>
Cr-Commit-Position: refs/heads/main@{#1503443}