patch: net: add socket read/write hooks

[mihaip]

Summary: lets us instrument all socket I/O so that we can see when it happens (and thus its effect on battery life). Upstream status: seems unlikely to be accepted Importance: instrumentation for mobile clients, not load-bearing/critical for app functionality. tailscale/corp#9230 has details Example prior commit: 62341525d56cbddada16161a3b12410f636f1051