CAS analytics no longer fsync per op, ending daemon starvation

The Xcode compilation cache (CAS) daemon no longer fsyncs its analytics sqlite database on every per-op metadata insert (PRAGMA synchronous=OFF). On hosted macOS runners this was ballooning CAS op latency because fsync contended with swiftc compilers writing object files; measured impact drops per-op CAS latency from ~573ms p50 to ~3.6ms under the same contention. CAS analytics are disposable per-build telemetry, so skipping fsync is safe; the main db still stays current via wal_autocheckpoint so the build-report upload copies it correctly.