Updates for .NET 8 - release-2.0

Set CI workflow dotnet-version to 8.0.x, 7.0.x, 6.0.x
Set release workflow dotnet-version to 8.0.x
Set test project target frameworks to (net481);net6.0;net7.0;net8.0
Set pwsh as default shell for CI and Release workflows
Use Particular/push-octopus-package-action@main with comment
Update GitHub Actions versions:
- actions/checkout to v4.1.1
- 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
- Particular.Approvals to 0.3.0 if using 0.2.0
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.Transport.AzureServiceBus