Add Kubernetes CTS

This adds patches and build specifications for the Kubernetes Conformance Test Suite. This involves
gating various cloud-specific tests behind the providerless flag (otherwise we'd gain a ton of additional dependencies)
and an additional 60MiB in test binary size.
Since the CTS for weird reasons requires kubectl to be available in the path we first build a kubectl go_image and then
stack the CTS on top of it. The output bundle is then preseeded for use.

Test Plan: `bazel run //core/tests/e2e/k8s_cts`

Bug: T836

X-Origin-Diff: phab/D615
GitOrigin-RevId: 7d2cd780a3ffb63b217591c5854b4aec4031d83d
diff --git a/core/BUILD b/core/BUILD
index 33ec07d..5d628f1 100644
--- a/core/BUILD
+++ b/core/BUILD
@@ -43,6 +43,7 @@
 
         # Containerd preseed bundles
         "//core/tests/e2e/preseedtest:preseedtest.tar": "/containerd/preseed/k8s.io/preseedtest.tar",
+        "//core/tests/e2e/k8s_cts:k8s_cts_image.tar": "/containerd/preseed/k8s.io/k8s_cts.tar",
 
         # CNI Plugins
         "@com_github_containernetworking_plugins//plugins/main/loopback": "/containerd/bin/cni/loopback",