ci: add a cpu and memory request

We're not currently requesting anything, which means we're at the mercy
of any default limit set on the cluster we're running on. Let's add an
explicit request.

Also bump the CPU request to 4 from the default of 2.

.cci.jenkinsfile

@@ -1,6 +1,7 @@
 // Documentation: https://github.com/coreos/coreos-ci/blob/main/README-upstream-ci.md
 
-cosaPod {
+// We run `kolaTestIso` which requires at least 8Gi. Add 512M for overhead.
+cosaPod(cpus: 4, memory: "8704Mi") {
     checkoutToDir(scm, 'config')
 
     def basearch = shwrapCapture("cosa basearch")