Add test for send_timeout_close

LH: I reworked the test a little and added the same test
for HTTP/2 so that both HTTP/1.1 and HTTP/2 get the issue
fixed.

test/handlers/loop_handler_endless_h.erl

@@ -0,0 +1,24 @@
+%% This module implements a loop handler that streams endless data.
+
+-module(loop_handler_endless_h).
+
+-export([init/2]).
+-export([info/3]).
+
+init(Req0, #{delay := Delay} = Opts) ->
+	case cowboy_req:header(<<"x-test-pid">>, Req0) of
+		BinPid when is_binary(BinPid) ->
+			Pid = list_to_pid(binary_to_list(BinPid)),
+			Pid ! {Pid, self(), init},
+			ok;
+		_ ->
+			ok
+	end,
+	erlang:send_after(Delay, self(), timeout),
+	Req = cowboy_req:stream_reply(200, Req0),
+	{cowboy_loop, Req, Opts}.
+
+info(timeout, Req, State) ->
+	cowboy_req:stream_body(<<0:1000/unit:8>>, nofin, Req),
+	erlang:send_after(10, self(), timeout),
+	{ok, Req, State}.