This enables a user to explicitly mark that there should be no fallback registry and also, as a natural consequence, allows a user to specify subsets of modules for which registry access is denied. Fixes #2963 Signed-off-by: Roger Peppe <rogpeppe@gmail.com> Change-Id: I8fdf7144b02fc61541bb28c8895c4cddf992f642 Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1193289 Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com> TryBot-Result: CUEcueckoo <cueckoo@cuelang.org> Reviewed-by: Daniel Martí <mvdan@mvdan.cc>