CLEANUP: lists/tree-wide: rename some list operations to avoid some confusion

The current "ADD" vs "ADDQ" is confusing because when thinking in terms
of appending at the end of a list, "ADD" naturally comes to mind, but
here it does the opposite, it inserts. Several times already it's been
incorrectly used where ADDQ was expected, the latest of which was a
fortunate accident explained in 6fa922562 ("CLEANUP: stream: explain
why we queue the stream at the head of the server list").

Let's use more explicit (but slightly longer) names now:

   LIST_ADD        ->       LIST_INSERT
   LIST_ADDQ       ->       LIST_APPEND
   LIST_ADDED      ->       LIST_INLIST
   LIST_DEL        ->       LIST_DELETE

The same is true for MT_LISTs, including their "TRY" variant.
LIST_DEL_INIT keeps its short name to encourage to use it instead of the
lazier LIST_DELETE which is often less safe.

The change is large (~674 non-comment entries) but is mechanical enough
to remain safe. No permutation was performed, so any out-of-tree code
can easily map older names to new ones.

The list doc was updated.
diff --git a/src/check.c b/src/check.c
index e3778ea..ee225a2 100644
--- a/src/check.c
+++ b/src/check.c
@@ -1273,11 +1273,11 @@
 {
 	struct buffer *buf = NULL;
 
-	if (likely(!LIST_ADDED(&check->buf_wait.list)) &&
+	if (likely(!LIST_INLIST(&check->buf_wait.list)) &&
 	    unlikely((buf = b_alloc(bptr)) == NULL)) {
 		check->buf_wait.target = check;
 		check->buf_wait.wakeup_cb = check_buf_available;
-		LIST_ADDQ(&ti->buffer_wq, &check->buf_wait.list);
+		LIST_APPEND(&ti->buffer_wq, &check->buf_wait.list);
 	}
 	return buf;
 }
@@ -1701,7 +1701,7 @@
 		}
 		chk->action = TCPCHK_ACT_CONNECT;
 		chk->connect.options = (TCPCHK_OPT_DEFAULT_CONNECT|TCPCHK_OPT_IMPLICIT);
-		LIST_ADD(srv->agent.tcpcheck_rules->list, &chk->list);
+		LIST_INSERT(srv->agent.tcpcheck_rules->list, &chk->list);
 	}
 
 
@@ -1874,7 +1874,7 @@
 		goto error;
 	}
 	chk->index = 0;
-	LIST_ADDQ(&rs->rules, &chk->list);
+	LIST_APPEND(&rs->rules, &chk->list);
 
 	chk = parse_tcpcheck_expect((char *[]){"tcp-check", "expect", "custom", ""},
 		                    1, curpx, &rs->rules, TCPCHK_RULES_AGENT_CHK,
@@ -1885,7 +1885,7 @@
 	}
 	chk->expect.custom = tcpcheck_agent_expect_reply;
 	chk->index = 1;
-	LIST_ADDQ(&rs->rules, &chk->list);
+	LIST_APPEND(&rs->rules, &chk->list);
 
   ruleset_found:
 	rules->list = &rs->rules;
@@ -1986,7 +1986,7 @@
 	var->data.u.str.area = str;
 	var->data.u.str.data = strlen(str);
 	LIST_INIT(&var->list);
-	LIST_ADDQ(&rules->preset_vars, &var->list);
+	LIST_APPEND(&rules->preset_vars, &var->list);
 
 	return 1;