Context

Move from targetting, deploying and mentioning net7.0 to net8.0
The targetting update was done here: #8468
Other locations to update: https://github.com/dotnet/msbuild/blob/main/Directory.Build.props#L18-L26

Updating the global.json might result to issues in tests - that is expected to be adressed as part of this item.

cc @rainersigwald to provide more context on expected scope and timing (as we already branched off the 17.7 - fliping to net8 targetting should be fine right away - correct?)