Consolidate .NET SDK versions to 10.0.x across all GitHub workflows (#5847)

## Description

Eight workflows install 2+ .NET SDK versions (combinations of 6.0.x,
8.0.x, 9.0.x alongside 10.0.x). All secondary versions are unnecessary —
.NET 10 SDK resolves older targeting packs via NuGet, self-contained
publishes bundle the runtime, and tools like CLOG/docfx support
roll-forward.

**Workflow changes** — remove secondary `dotnet-version` entries,
keeping only `10.0.x`:

- `check-clog.yml`: drop 8.0.x (CLOG already sets
`DOTNET_ROLL_FORWARD=Major`)
- `publish-docfx.yml`: drop 8.x (global tools roll forward natively)
- `check-dotnet.yml`, `dotnet-test.yml`, `plugins.yml`: drop 6.0.x (SDK
builds net6.0/netcoreapp3.1/netstandard targets via NuGet targeting
packs)
- `package-linux.yml`, `package-alpine-linux.yml`,
`validate-linux-packages-reuse.yml`: drop 9.0.x (self-contained publish
includes runtime in output)
- `plugins.yml`: add `DOTNET_ROLL_FORWARD: LatestMajor` to the Package
step so the `plugintool` global tool (which targets net6.0) runs on the
.NET 10 runtime instead of requiring .NET 6 to be installed.

**Project change:**

- `src/cs/tool/MsQuicTool.csproj`: `net6.0` → `net10.0`. This is an
internal test tool (not published), and `dotnet run` requires a matching
runtime. The library `msquic.csproj` multi-targeting
(net6.0/netstandard2.0/netstandard2.1) is unchanged.

## Testing

All existing CI workflows cover these changes — they exercise the exact
build/run paths affected. No new tests needed.

## Documentation

No documentation impact.

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.github/workflows/check-clog.yml

@@ -22,9 +22,7 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@baa11fbfe1d6520db94683bd5c7a3818018e4309
       with:
-        dotnet-version: |
-          10.0.x
-          8.0.x
+        dotnet-version: 10.0.x
     - name: Checkout repository
       uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
     - name: Prepare Machine

.github/workflows/check-dotnet.yml

@@ -22,9 +22,7 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@baa11fbfe1d6520db94683bd5c7a3818018e4309
       with:
-        dotnet-version: |
-          10.0.x
-          6.0.x
+        dotnet-version: 10.0.x
     - name: Checkout repository
       uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
     - name: Prepare Machine

.github/workflows/dotnet-test.yml

@@ -101,9 +101,7 @@ jobs:
         path: artifacts
     - uses: actions/setup-dotnet@baa11fbfe1d6520db94683bd5c7a3818018e4309
       with:
-        dotnet-version: |
-          10.0.x
-          6.0.x
+        dotnet-version: 10.0.x
     - name: Run Lang Interop
       shell: pwsh
       run: scripts/DotNetTest.ps1 -Config Debug -Arch ${{ matrix.vec.arch }} -Tls ${{ matrix.vec.tls }} -DomainName "google.com"

.github/workflows/package-alpine-linux.yml

@@ -72,12 +72,10 @@ jobs:
         path: artifacts
     - name: Set up QEMU
       uses: docker/setup-qemu-action@c7c53464625b32c7a7e944ae62b3e17d2b600130
-    - name: Set up .NET 9.0
+    - name: Set up .NET
       uses: actions/setup-dotnet@baa11fbfe1d6520db94683bd5c7a3818018e4309
       with:
-        dotnet-version: |
-          10.0.x
-          ${{ matrix.vec.dotnetVersion }}
+        dotnet-version: 10.0.x
     - name: Build .NET QUIC Test Project (self-contained)
       run: |
         # Map arch to musl runtime identifier

.github/workflows/package-linux.yml

@@ -153,9 +153,7 @@ jobs:
     - name: Set up .NET
       uses: actions/setup-dotnet@baa11fbfe1d6520db94683bd5c7a3818018e4309
       with:
-        dotnet-version: |
-          10.0.x
-          9.0.x
+        dotnet-version: 10.0.x
     - name: Build .NET QUIC Test Projects (Self-Contained)
       run: |
         # Map arch to runtime identifier

.github/workflows/plugins.yml

@@ -53,9 +53,7 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@baa11fbfe1d6520db94683bd5c7a3818018e4309
       with:
-        dotnet-version: |
-          10.0.x
-          6.0.x
+        dotnet-version: 10.0.x
     - name: Install Dependencies
       run: dotnet tool install --global Microsoft.Performance.Toolkit.Plugins.Cli --version 0.1.25-preview
     - name: Build
@@ -66,6 +64,8 @@ jobs:
         path: artifacts/bin/quictrace/${{ matrix.configuration }}
     - name: Package
       shell: pwsh
+      env:
+        DOTNET_ROLL_FORWARD: LatestMajor
       run: |
         $sourceDir = "src\plugins\trace\dll\bin\${{ matrix.configuration }}\netstandard2.1"
         $manifestPath = "$sourceDir/pluginManifest.json"

.github/workflows/publish-docfx.yml

@@ -33,9 +33,7 @@ jobs:
     - name: Dotnet Setup
       uses: actions/setup-dotnet@baa11fbfe1d6520db94683bd5c7a3818018e4309
       with:
-        dotnet-version: |
-          10.0.x
-          8.x
+        dotnet-version: 10.0.x
 
     - run: dotnet tool update -g docfx
     - run: chmod +x ./scripts/prepare-docfx.ps1

.github/workflows/validate-linux-packages-reuse.yml

@@ -89,9 +89,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@baa11fbfe1d6520db94683bd5c7a3818018e4309
         with:
-          dotnet-version: |
-            10.0.x
-            9.0
+          dotnet-version: 10.0.x
 
       - name: Build QuicHello
         run: |

src/cs/tool/MsQuicTool.csproj

@@ -6,7 +6,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>