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/alpine/tests/alpine.cue

@@ -0,0 +1,43 @@
+package alpine
+
+import (
+	"alpha.dagger.io/dagger/op"
+)
+
+TestImageVersion: {
+	image: #Image & {
+		// install an old version on purpose
+		version: "3.10.9"
+	}
+
+	test: #up: [
+		op.#Load & {from: image},
+		op.#Exec & {
+			args: [
+				"sh",
+				"-ec",
+				"""
+					test "$(cat /etc/alpine-release)" = 3.10.9
+					""",
+			]
+		},
+	]
+}
+
+TestPackageInstall: {
+	image: #Image & {
+		package: jq:   true
+		package: curl: true
+		version: "3.15.0"
+	}
+
+	test: #up: [
+		op.#Load & {from: image},
+		op.#Exec & {
+			args: ["jq", "--version"]
+		},
+		op.#Exec & {
+			args: ["sh", "-ec", "curl --version"]
+		},
+	]
+}