Echoserver Channel Regrouping

Refactor of the echoserver example only; library is unchanged.

1. Collapse FwdStates and AGENT_STATE_* into a single WS_AppState
   (INIT/LISTEN/CONNECT/CONNECTED). FWD_STATE_DIRECT becomes an
   isDirect flag, cleared after connect.
2. Hoist the fields shared by the forwarding, agent, and shell paths
   into a common WS_AppCtx (privateData, listenFd, appFd, channelId,
   state, buffer). Shell only uses buffer.
3. Feature-specific remainder stays in WS_AgentCbActionCtx (name) and
   WS_FwdCbActionCtx (host/origin name+port, isDirect). Drop the unused
   pid field; inline getpid() at the call site.
4. wolfSSH_AGENT_DefaultActions and wolfSSH_FwdDefaultActions now take
   a WS_AppCtx* and reach feature-specific state via
   appCtx->privateData. echoserver_test() is updated to register the
   WS_AppCtx (not the old CbCtx) with wolfSSH_set_agent_cb_ctx and
   wolfSSH_SetFwdCbCtx.
5. Reindent ssh_worker()'s #ifdef blocks and add /* WOLFSSH_xxx */
   markers.
6. fwd.test.expect: redirect echoserver and portfwd output to log files
   and sync on portfwd's -R ready file instead of matching "sampled" in
   the pty. Under --enable-debug the WLOG volume fills the pty and
   stalls portfwd in select() before channel-open.

Author: ejohnstown