SDK Diff pipeline should discover artifacts from upstream builds with post-build failures

When a post-build step (1ESPT, signing, etc.) fails in the upstream pipeline, artifacts get published under a failure/alternate name instead of the expected name (e.g. `SB_Ubuntu2404_Offline_MsftSdk_x64_Artifacts`). The SDK Diff pipeline does a strict name lookup, can't find them, and fails — even though the SDK was successfully built.

The artifact download logic should fall back to enumerating available artifacts on the upstream build and matching by pattern when the expected name isn't found.

Example: [SDK Diff build 2950719](https://dev.azure.com/dnceng/7ea9116e-9fac-403d-b258-b31fcf1bb293/_build/results?buildId=2950719) failed because [upstream build 2950508](https://dev.azure.com/dnceng/7ea9116e-9fac-403d-b258-b31fcf1bb293/_build/results?buildId=2950508) had a post-build failure.