GitHub-CI (CodeQL, windows): Use windows-latest runner image.

* .github/workflows/codeql-analysis.yaml (windows): "windows-2019" has been
deprecated and dropped. Use the "windows-latest" image again. This essentially
reverts ffed0ae35eda. Also add a workflow dispatch trigger to be able to run
the workflow on demand.

See: actions/runner-images#12045

Author: mmuetzel

.github/workflows/codeql-analysis.yaml

@@ -4,6 +4,7 @@ on:
   schedule:
     # Run job every Monday and Thursday at 16:30 UTC
     - cron: '30 16 * * 1,4'
+  workflow_dispatch:
 
 jobs:
   ubuntu:
@@ -68,7 +69,7 @@ jobs:
 
   windows:
     name: CodeQL analysis (Windows)
-    runs-on: windows-2019
+    runs-on: windows-latest
 
     defaults:
       run: