Replace Azure DevOps pipelines with GitHub Actions

Add CI workflow (build + test on PRs and master pushes) and a publish
workflow that pushes to NuGet on GitHub releases. Remove the old Azure
DevOps pipeline YAMLs and Cake build scripts which referenced obsolete
VM images (ubuntu-16.04, vs2017-win2016).

The publish workflow requires a NUGET_API_KEY repository secret.

https://claude.ai/code/session_01GqyDyB2zrpxr1ZVw8vFVg3

Author: claude

.github/workflows/ci.yml

@@ -0,0 +1,28 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  build-and-test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '8.0.x'
+
+      - name: Restore dependencies
+        run: dotnet restore
+
+      - name: Build
+        run: dotnet build --configuration Release --no-restore
+
+      - name: Test
+        run: dotnet test --configuration Release --no-build --verbosity normal

.github/workflows/publish.yml

@@ -0,0 +1,32 @@
+name: Publish to NuGet
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '8.0.x'
+
+      - name: Restore dependencies
+        run: dotnet restore
+
+      - name: Build
+        run: dotnet build --configuration Release --no-restore
+
+      - name: Test
+        run: dotnet test --configuration Release --no-build --verbosity normal
+
+      - name: Pack
+        run: dotnet pack src/IpData/IpData.csproj --configuration Release --no-build --output ./nupkg
+
+      - name: Publish to NuGet
+        run: dotnet nuget push ./nupkg/*.nupkg --api-key ${{ secrets.NUGET_API_KEY }} --source https://api.nuget.org/v3/index.json --skip-duplicate