chore(ci) add kong-3.x and dispatch triggers for the test workflows

Add kong-3.x release branch to the PR checks conditions.

Add dispatch option to the PR checks because ey why not. Having the
ability to run tests on things that aren't normally in the trigger
pipeline is useful.

.github/workflows/release-pr.yaml

@@ -11,7 +11,9 @@ on:
     branches:
       - main
       - release/kong-2.x
+      - release/kong-3.x
       - prepare-kgo-chart
+    workflow_dispatch: {}
 
 env:
   # Specify this here because these tests rely on ktf to run kind for cluster creation.