Update project framework targets: Remove net6.0/net7.0, add net10.0, update net9.0-only to net10.0

[Copilot]

This PR updates all project framework targets in the grpc-dotnet repository to align with the latest .NET roadmap and remove support for out-of-support framework versions.

Changes Made

Framework Target Updates

• Removed .NET 6.0 and .NET 7.0 targets from all projects (both are approaching or have reached end-of-support)
• Added .NET 10.0 targets to multi-target framework projects
• Updated single-target projects from .NET 9.0 to .NET 10.0

Specific Patterns Updated

Multi-target projects (src libraries, test projects):

<!-- Before -->
<TargetFrameworks>net6.0;net7.0;net8.0;net9.0</TargetFrameworks>

<!-- After -->
<TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>

Single-target projects (examples, tools, benchmarks):

<!-- Before -->
<TargetFramework>net9.0</TargetFramework>

<!-- After -->
<TargetFramework>net10.0</TargetFramework>

Legacy test projects:

<!-- Before -->
<TargetFrameworks>net462;net6.0</TargetFrameworks>

<!-- After -->
<TargetFrameworks>net462;net8.0;net9.0;net10.0</TargetFrameworks>

Conditional References Updated

• Updated PropertyGroup conditions to replace net6.0/net7.0 checks with net8.0/net9.0/net10.0
• Consolidated framework-specific ItemGroups to remove obsolete package version overrides
• Maintained backward compatibility for .NET Framework 4.6.2 and .NET Standard 2.x targets where appropriate

SDK Configuration

• Updated global.json to use .NET 10.0 preview SDK (10.0.100-preview.6.25358.103)

Impact

• 92 projects now target .NET 10.0
• 0 projects still reference .NET 6.0 or .NET 7.0
• Maintains compatibility with existing supported frameworks (.NET 8.0, .NET 9.0, .NET Framework 4.6.2, .NET Standard 2.x)
• Ensures the repository stays current with Microsoft's .NET support lifecycle

Fixes #2651.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• aka.ms
  • Triggering command: curl -I -sSL --retry 5 --retry-delay 2 --connect-timeout 15 REDACTED (dns block)
• grpc.jfrog.io
  • Triggering command: dotnet build -c Release --verbosity quiet (dns block)
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)
  • Triggering command: dotnet build examples/Counter/Server/Server.csproj -c Release (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

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