When attempting to update existing codeflow PRs, we incorrectly update the `InProgressPullRequest`

[dkurepa]

If a subscription has an already open PR and a subscription is triggered, but no changes to flow are detected, we still proceed to update the in progress pull request, even tho we didn't update the PR.
When we do this we update the ContainedSubscriptions property, and set the build id of the build we tried flowing, but determined we shouldn't.

The codeflow check reads this property later, and compares it with the build in the repo, and turns red when they don't align

[adamzip]

Seems like there could be two ways to fix it

1. Do not update ContainedSubscriptions on a no-updates flow
2. Keep it as it is, but also update source-manifest or Version.Details.xml with the id of the "no-op" build.

I think the second option is more informative and maybe more "correct" - instead of having tried to flow the build but then erasing all signs that we tried to flow it, we just make it explicit that it is the last build that was flowed, even if it didn't have any additional updates on top of what had already been flowed. But it would require to change some of the logic we have around codeflows with updates, and pushing of branches and such

[dkurepa]

I don't agree, the second option is definitely wrong, since that commit is not what's in the VMR/repo. We shouldn't be updating the InProgressPullRequest, because then we'll also push meaningless commits that are just changing the metadata