Move dnceng repositories to .NET 8

[garath]

The release of .NET 8 reminds us that the EOL dates for .NET 6 and 7 approach. Most of dnceng repositories are using .NET 6, but a few are using .NET 7, and that date is close enough to start thinking about allocating time to focus on an update.

.NET 6 leaves support on November 12, 2024. .NET 7 leaves support on May 14, 2024.

Repository	Framework	Tracking or Change
dotnet/dnceng	net6.0
dotnet/dnceng-shared	net6.0
dotnet-helix-service	net7.0	#2413
✅ dotnet-helix-machines	net8.0	!35018
✅ dotnet-migrate-package	net8.0	!39070

Release Note Category

• Feature changes/additions
• Bug fixes
• Internal Infrastructure Improvements

Release Note Description

Migrate repository to .NET 8

[missymessa]

When we are ready to do this work, split out into individual issues per repo because it's a lot of work for just one issue.

[premun]

Is the goal to move 6.0 SDK like dnceng for instance, where I did that already, or to target the 8.0 TFM?

Some repos are easy, like dotnet-migrate-package, but repos like dnceng-shared provide libraries for Service Fabric which I think does not support 8.0 yet so I am not sure what we should do there.
microsoft/service-fabric#1472

[chcosta]

Is the goal to move 6.0 SDK like dnceng for instance, where I did that already, or to target the 8.0 TFM?

I think that both are relevant. Repos using a 6.0 / 7.0 SDK should move to 8.0, and they should target the 8.0 TFM. Does anyone else have a different interpretation?

For reference: https://dotnet.microsoft.com/en-us/platform/support/policy/dotnet-core

[chcosta]

repos like dnceng-shared provide libraries for Service Fabric which I think does not support 8.0 yet

Looks like the latest is that they hope to have support for 8.0 in April (though they lack confidence in this timeline).

dotnet-migrate-package and dotnet-helix-service are more immediately pressing for moving to .NET 8.

[missymessa]

I think we need to do #2341 before we can do this issue.