Parameterize K8s version in node-e2e workflow

Add inputs to workflow_call in node-e2e.yml to allow specifying
Kubernetes branch or tag to test against. Update checkout step
to use this input, defaulting to master.

This enables testing containerd against specific Kubernetes release
branches, which is required for verifying compatibility with extended
support windows for Kubernetes distros that require them.

Signed-off-by: Chris Henzie <chrishenzie@gmail.com>
Assisted-by: Antigravity

.github/workflows/node-e2e.yml

@@ -1,7 +1,12 @@
 name: E2E
 on:
   workflow_call:
-
+    inputs:
+      k8s_version:
+        description: 'Kubernetes branch or tag to test against'
+        required: false
+        default: 'master'
+        type: string
 permissions:
   contents: read
 
@@ -41,6 +46,7 @@ jobs:
         with:
           repository: kubernetes/kubernetes
           path: src/k8s.io/kubernetes
+          ref: ${{ inputs.k8s_version }}
           fetch-depth: 0
 
       - name: Install Go