Updates for .NET 8 - release-4.3

Set CI workflow dotnet-version to 8.0.x
Set release workflow dotnet-version to 8.0.x
Set test project target frameworks (not including .NET Framework) to net8.0
Update GitHub Actions versions:
- actions/checkout to v4.1.2
- actions/setup-dotnet to v4.0.0
- actions/upload-artifact to v4.3.1
- Particular/run-tests-action to v1.7.0
- Particular/push-octopus-package-action to v2.0.0
- azure/login to v2.0.0
Update build tool NuGet package versions in test projects:
- GitHubActionsTestLogger to 2.3.3
- Microsoft.NET.Test.Sdk to 17.9.0
- NUnit to 3.14.0
- NUnit3TestAdapter to 4.5.0

Particular / NServiceBus.AzureFunctions.InProcess.ServiceBus