List all installed modules that need updates.

Usage:
  v outdated

Projects using version ranges report Current / Upgradable / Resolvable / Latest:
Current is installed; Upgradable obeys the installed graph's requirements;
Resolvable solves the complete graph again; Latest ignores project constraints.
The report reads remote release tags and manifests without changing checkouts
or v.mod.lock. Other projects retain the branch-based report.
