Apple graph support with query, build, run, and test commands

Once can now build, run, and test Apple targets from the same graph-aware, cacheable workflow used for other ecosystems. Use once query targets to list available targets, once query capabilities and once query schema to inspect the Apple target contract, and once build, once run, or once test to materialize and launch apps or run tests. The Apple target kinds include apple_library for Swift, Objective-C, C, and C++ static libraries, swift_macro for compiler plugins, and graph-level target kinds such as apple_framework, apple_application, and apple_test_bundle for bundles, apps, and test hosts. Outputs are written under .once/out//. Apple targets also support declarative select-style configuration per platform, architecture, SDK variant, and mac_catalyst, so a single target can use,