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/bats/tests/testfile/mods/bats-support/script/install-bats.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+set -o errexit
+set -o xtrace
+
+git clone --depth 1 https://github.com/sstephenson/bats
+cd bats && ./install.sh "${HOME}/.local" && cd .. && rm -rf bats