fix: report worker activity to pg_stat_activity

Background workers must call pgstat_report_activity() themselves to
update state/state_change in pg_stat_activity; regular user backends
get this for free via tcop/postgres.c. Without it the pg_net worker
shows up with a blank state column, making it impossible to tell
from monitoring whether the worker is idle, processing a tick, or
stuck in a transaction. Adds STATE_IDLE / STATE_RUNNING transitions
around the inner work loop.

cmd_str is NULL, matching what other background workers (e.g.
logical replication apply worker) do; backend_type already
identifies it as "pg_net <ver> worker" so a query-column label
would be redundant.

Author: utkarash2991

src/worker.c

@@ -265,6 +265,9 @@ void pg_net_worker(__attribute__((unused)) Datum main_arg) {
 
   publish_state(WS_RUNNING);
 
+  // Initial state: we go straight into the outer loop and wait for a wake.
+  pgstat_report_activity(STATE_IDLE, NULL);
+
   do {
 
     uint32 expected = 1;
@@ -274,6 +277,8 @@ void pg_net_worker(__attribute__((unused)) Datum main_arg) {
       continue;
     }
 
+    pgstat_report_activity(STATE_RUNNING, NULL);
+
     uint64 requests_consumed = 0;
     uint64 expired_responses = 0;
 
@@ -388,6 +393,9 @@ void pg_net_worker(__attribute__((unused)) Datum main_arg) {
 
     } while (!worker_should_restart && (requests_consumed > 0 || expired_responses > 0));
 
+    // Inner loop drained; back to waiting for the next wake.
+    pgstat_report_activity(STATE_IDLE, NULL);
+
   } while (!worker_should_restart);
 
   publish_state(WS_EXITED);