Refactor CI workflow to use a matrix strategy for builds and update Ubuntu version

Author: AGiorgetti

.github/workflows/ci.yml

@@ -18,9 +18,13 @@ concurrency:
 jobs:
   # Keep the Windows build separate so we still validate the .NET Framework target
   # and the packaging prerequisites that only exist on Windows runners.
-  build-windows:
-    name: Build (Windows)
-    runs-on: windows-latest
+  build:
+    name: Build (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
 
     steps:
       - name: Checkout
@@ -68,7 +72,7 @@ jobs:
   # The matrix is therefore per target framework instead of per OS.
   test-modern-tfm-linux:
     name: Test (Linux, ${{ matrix.tfm }})
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix: