Two small changes:
- In our BYONM errors, suggest running `deno install` instead of `npm
install` if `DENO_FUTURE` is set
- Only emit warning about `deno install` changes if you do `deno install
<foo>` with deno_future unset
Closes #18296.
Adds a `--frozen` (alias `--frozen-lockfile`) flag that errors out if
the lockfile is out of date. This is useful for running in CI (where an
out of date lockfile is usually a mistake) or to prevent accidental
changes in dependencies.
