BARViz should show last flow sha for each UB build

[mmitche]

Goal:
For VMR builds, display a table showing the contents of the VMR's source-manifest at the build's commit.

Implementation:

• Create a new API endpoint in ProductConstructionService that returns the contents of src/source-manifest.json for a given repo url and commit SHA. It should use the existing method named GetSourceManifestAsync defined at \src\Microsoft.DotNet.Darc\DarcLib\Remote.cs
• Query that same source-manifest endpoint from the BuildInfo.razor page in BarVIZ, providing the git repo url as well as the build's commit SHA as arguments.
• If the fetched source-manifest data is not null or empty, display the contents in the BuildInfo.razor page as a table.

For reference, here is an example of an entry in the source-manifest:

 {
   "barId": 272559,
   "path": "cecil",
   "remoteUri": "https://github.com/dotnet/cecil",
   "commitSha": "48fe72b0bcb273476e3f480bb61f42c5dd295131"
 },

[premun]

@mmitche the codeflows page now shows the SHAs and for the build information the SHA is here:

Is that enough?

[mmitche]

The codeflows is "latest" information. I think it would be super useful if the build page listed the last flowed for that specific build.

[premun]

We clarified Matt's ask and basically we want to add a new table on the build page for VMR builds which would basically show the source manifest from the commit of the VMR build and for each SHA in the source manifest, we'd ideally get the associated build from each repo.

[adamzip]

This looks like a good candidate for Copilot to do most of the work on, so I'll rewrite the title and description a bit