cue/load: add initial module.cue schema
This adds the module.cue file format definition and verifies against it
when loading the configuration. We only add the existing single `module`
field for now.
I've added some tests that show the errors resulting from a bad module.cue
file look reasonable, which necessitated reshuffling the existing
test data around a bit.
Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: I7339b96df9c195eeb02fda5197e790d15a6aad1d
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/549008
Unity-Result: CUEcueckoo <cueckoo@cuelang.org>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>