Upstream connection events, EOF and I/O errors are never propagated to network filters #13940
Description
The read/write network filters never receive information about:
- upstream connection events (connected, local/remote close),
- mid-stream I/O errors (see: Mid-stream I/O errors are silently ignored in TCP proxy and other network filters #13939),
- EOF (in case of connections without half-close semantics),
which significantly limits robustness and capabilities of WebAssembly and ext_proc extensions.