ci: install .NET 8 SDK in CI and builds

Author: mjcheetham

.github/workflows/codeql-analysis.yml

@@ -29,6 +29,11 @@ jobs:
       with:
         dotnet-version: 8.0.x
 
+    - name: Setup .NET
+      uses: actions/setup-dotnet@v3.2.0
+      with:
+        dotnet-version: 8.0.x
+
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v4