[v9] Don't rely on Next.js Build ID for release names

[lforst]

Description

The future of the availability of the Next.js Build ID is uncertain with Turbopack. In preparation, we should not rely on it for release names and instead attempt to use git commit shas. As an added benefit, the Build ID was non-deterministic and caused issues for users who relied on deterministic builds (it also caused cache busts).

The history of thoughts around this change is outlined in this comment: #14303 (comment)