ci: bump EOL Fedora versions to 42/43 (#13206)

Fedora 39 (EOL 2024-11-26), Fedora 40 (EOL 2025-05-13), and Fedora 41
(EOL 2025-12-15) are all out of support and no longer receive security
updates. This bumps the kubevirt CI test matrix to currently supported
releases, distributing tests across Fedora 42 (supported until
2026-05-13) and Fedora 43 (supported until 2026-12-09) to keep
multi-version coverage.

- Add fedora-43 image entry to the kubevirt image-builder
- Rename fedora39-* tests to fedora43-* (4 tests)
- Rename fedora40-* tests to fedora43-* (2 tests)
- Rename fedora41-* tests to fedora42-* (4 tests)
- Update .gitlab-ci/kubevirt.yml testcase names
- Regenerate docs/developers/ci.md

All 10 existing Fedora test configurations (kube-router, calico-selinux,
calico-swap-selinux, crio with/without SELinux enforcing, docker-calico,
flannel-crio-collection-scale) are preserved.

Signed-off-by: Kay Yan <kay.yan@daocloud.io>

test-infra/image-builder/roles/kubevirt-images/defaults/main.yml

@@ -73,6 +73,13 @@ images:
     converted: true
     tag: "latest"
 
+  fedora-43:
+    filename: Fedora-Cloud-Base-Generic-43-1.6.x86_64.qcow2
+    url: https://download.fedoraproject.org/pub/fedora/linux/releases/43/Cloud/x86_64/images/Fedora-Cloud-Base-Generic-43-1.6.x86_64.qcow2
+    checksum: sha256:846574c8a97cd2d8dc1f231062d73107cc85cbbbda56335e264a46e3a6c8ab2f
+    converted: true
+    tag: "latest"
+
   fedora-coreos:
     filename: fedora-coreos-32.20200601.3.0-openstack.x86_64.qcow2.xz
     url: https://builds.coreos.fedoraproject.org/prod/streams/stable/builds/32.20200601.3.0/x86_64/fedora-coreos-32.20200601.3.0-openstack.x86_64.qcow2.xz