[ruby/net-http] Enforce write timeout when body_stream is used

The existing implementation of `Net::HTTP#write_timeout` relies on
`Net::BefferedIO` to trigger the `Net::WriteTimeout` error. This commit
changes `send_request_with_body_stream` to remove the optimization that
was making `Net::HTTP#write_timeout` not work when `body_stream` is
used.

Open issue:
https://bugs.ruby-lang.org/issues/17933

a0fab1ab52

test/net/http/test_http.rb

@@ -576,6 +576,34 @@ module TestNetHTTP_version_1_1_methods
     th&.join
   end
 
+  def test_timeout_during_non_chunked_streamed_HTTP_session_write
+    th = nil
+    # listen for connections... but deliberately do not read
+    TCPServer.open('localhost', 0) {|server|
+      port = server.addr[1]
+
+      conn = Net::HTTP.new('localhost', port)
+      conn.write_timeout = 0.01
+      conn.read_timeout = 0.01 if windows?
+      conn.open_timeout = 0.1
+
+      req = Net::HTTP::Post.new('/')
+      data = "a"*50_000_000
+      req.content_length = data.size
+      req['Content-Type'] = 'application/x-www-form-urlencoded'
+      req.body_stream = StringIO.new(data)
+
+      th = Thread.new do
+        err = !windows? ? Net::WriteTimeout : Net::ReadTimeout
+        assert_raise(err) { conn.request(req) }
+      end
+      assert th.join(10)
+    }
+  ensure
+    th&.kill
+    th&.join
+  end
+
   def test_timeout_during_HTTP_session
     bug4246 = "expected the HTTP session to have timed out but have not. c.f. [ruby-core:34203]"