Merge samples changes from main to nightly

[lbussell]

This includes all samples changes since and including #4742, and my changes to sample image test data from #4890.

• Update samples to .NET 8 (Update samples to .NET 8 #4742)
• Update ENTRYPOINT of releasesapp sample (Update ENTRYPOINT of releasesapp sample #4874)
• Add nuget.config for nightly feed (Add nuget.config for nightly feed #4876)
• Update README.md (Update README.md #4880)
• Fix bad math (Fix bad math #4879)
• Update releasesapi nuget.config (Update releasesapi nuget.config #4887)
• Write indented JSON (Write indented JSON #4888)
• Remove package install (Remove package install #4882)
• Add Jammy Chiseled to sample image data
• Update unpublished sample image data
• Update formatting