Add git sha tags for net10.0 images

[sbomer]

We need to update the LLVM version used in our build images. As discussed in #1371, we would like a long-term solution where dotnet/runtime references images by sha, and they get updated via dependency flow PRs. In the meantime, we can temporarily pin dotnet/runtime images to a specific version to avoid build instability while we roll out new images for #1369.

This change adds back git sha based tags to make it easier to manually pin the images (not to a specific build, but to a specific sha - should be good enough for our purposes).