Add Apple graph query and materialization commands

New CLI commands let you inspect and materialize the Apple graph. once query targets, once query capabilities, and once query schema expose the graph’s targets and schemas. once build, once run, and once test are cache-backed commands that materialize artifacts under .once/out//. For example, once build for an apple_application produces a .app bundle and dSYMs, while once run consumes the bundle and once test produces test results and coverage for test bundles.