REORG: thread/sched: move the last dynamic thread_info to thread_ctx

The last 3 fields were 3 list heads that are per-thread, and which are:
  - the pool's LRU head
  - the buffer_wq
  - the streams list head

Moving them into thread_ctx completes the removal of dynamic elements
from the struct thread_info. Now all these dynamic elements are packed
together at a single place for a thread.
diff --git a/src/proxy.c b/src/proxy.c
index db876e6..6868eff 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -2017,7 +2017,7 @@
 	thread_isolate();
 
 	for (thr = 0; thr < global.nbthread; thr++) {
-		list_for_each_entry(s, &ha_thread_info[thr].streams, list) {
+		list_for_each_entry(s, &ha_thread_ctx[thr].streams, list) {
 			stream_shutdown(s, SF_ERR_KILLED);
 		}
 	}