Fix/687 - NativeAoT Support by upgrading to Dotnet 8 (lts) and implementing System.Text.Json source generation

[ThaDaVos]

These changes should allow one to use the project with NativeAoT as it now uses the latest LTS (Dotnet 8) and includes source generation for System.Text.Json.

Only thing I noticed after getting all System.Text.Json stuff working while setting <JsonSerializerIsReflectionEnabledByDefault>false</JsonSerializerIsReflectionEnabledByDefault> in my project - is that I get an error from the grpc package used:

Exception has occurred: CLR/Grpc.Core.RpcException
An exception of type 'Grpc.Core.RpcException' occurred in Pulumi.dll but was not handled in user code: 'Status(StatusCode="Unimplemented", Detail="")'
   at Pulumirpc.LanguageRuntime.LanguageRuntimeBase.GetRequiredPackages(GetRequiredPackagesRequest request, ServerCallContext context) in {PROJECT_PATH}\pulumi-dotnet\sdk\Pulumi\obj\Debug\net8.0\pulumi\LanguageGrpc.cs:line 311
   at Grpc.Shared.Server.UnaryServerMethodInvoker`3.Invoke(HttpContext httpContext, ServerCallContext serverCallContext, TRequest request)

Which I cannot figure out the actual cause of

[Copilot]

Pull Request Overview

This PR upgrades the Pulumi .NET SDK from .NET 6.0 to .NET 8.0 and updates numerous dependencies to their latest versions. The changes modernize the codebase with C# 12 features including collection expressions, primary constructors, and improved null checks.

Key changes:

• Upgrade target framework from net6.0 to net8.0 across all projects
• Update semver package from v2.1.0 to v3.0.0 (requires API changes due to removed IComparable interface)
• Update multiple Grpc, Microsoft, and other NuGet packages to latest versions
• Modernize C# code with collection expressions ([] syntax), ArgumentNullException.ThrowIfNull(), and other C# 12 features
• Add source generation context for JSON serialization performance improvements

Reviewed Changes

Copilot reviewed 35 out of 37 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
sdk/Pulumi/Pulumi.csproj	Updates target framework to net8.0 and dependencies to latest versions
sdk/Pulumi/Serialization/ResourcePackages.cs	Adapts SemVer usage to v3.0 API (CompareSortOrderTo instead of comparison operators)
sdk/Pulumi/Stack.cs	Replaces .Any() with .Count != 0 for performance
sdk/Pulumi/Core/Output.cs	Modernizes null checks and adds cached JsonSerializerOptions
sdk/Pulumi/Deployment/*.cs	Modernizes argument validation and string operations
sdk/Pulumi.Automation/*.cs	Updates to collection expressions and SemVer v3.0 API
sdk/Pulumi.Automation/Serialization/*.cs	Adds source generation for JSON serialization
Test projects	Updates test dependencies to latest versions
PublicAPI files	Adds nullable reference type annotations

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[Frassle]

Upgrade target framework from net6.0 to net8.0 across all projects

We'll have to think about this. We don't officially support net6 anymore (neither does Microsoft) but it is still a breaking change. I'll see if we can collect some data to see if we're likely to break anyone doing this.

[ThaDaVos]

@Frassle - why not release it as a new major version? Also, as far as I know, if the Dotnet version is bumped, older dotnet based projects shouldn't pull it anyway (as far as I know).

That aside, how can I fix the protobuf "not implemented" issue? That way I could build it locally and use it for myself at least.

[ThaDaVos]

Just got my GRPC issue fixed, I missed the -p:PulumiSdkVersion=3.205.0 - this is needed it seems.
Also noticed I missed a JsonSerializer.Serialize call and added this one too