Fixes #23571.
Previously, we required a `deno.json` to be present (or the `--lock`
flag) in order for us to resolve a `deno.lock` file. This meant that if
you were using deno in an npm-first project deno wouldn't use a
lockfile.
Additionally, while I was fixing that, I discovered there were a couple
bugs keeping the future `install` command from using a lockfile.
With this PR, `install` will actually resolve the lockfile (or create
one if not present), and update it if it's not up-to-date. This also
speeds up `deno install`, as we can use the lockfile to skip work during
npm resolution.
