cue modules: move stdlib to pkg/alpha.dagger.io

In preparation for Europa, we will vendor multiple CUE modules:

- `pkg/alpha.dagger.io`: legacy non-europa packages
- `pkg/dagger.io`: core Europa packages
- `pkg/universe.dagger.io`: Europa universe

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

pkg/alpha.dagger.io/docker/tests/push/push.cue

@@ -0,0 +1,36 @@
+package docker
+
+import (
+	"alpha.dagger.io/dagger"
+	"alpha.dagger.io/random"
+)
+
+TestRegistry: {
+	username: dagger.#Input & {string}
+	secret:   dagger.#Input & {dagger.#Secret}
+}
+
+TestPush: {
+	// Generate a random string
+	// Seed is used to force buildkit execution and not simply use a previous generated string.
+	tag: random.#String & {seed: "docker push"}
+
+	target: "daggerio/ci-test:\(tag.out)"
+
+	image: #Build & {
+		dockerfile: """
+				FROM alpine
+				RUN echo "test" > /test.txt
+			"""
+		source: ""
+	}
+
+	push: #Push & {
+		"target": target
+		source:   image
+		auth: {
+			username: TestRegistry.username
+			secret:   TestRegistry.secret
+		}
+	}
+}