connect_timeout is applied per resolved address, not per endpoint

`connect_stream` applies `connect_timeout` **per resolved address**, not per endpoint, contradicting the doc comment ("TCP connect timeout per endpoint attempt"). A hostname resolving to two addresses multiplies every bound: measured 2.0011s for two blackhole addresses at a 1s timeout.

Fix: give `connect_stream` a single total deadline across all resolved addresses, so the timeout bounds the endpoint attempt as documented.

首先阅读 connect_stream 及其 connect_timeout 文档注释，然后复现 issue 中描述的双地址情况，以确认当前按地址计算的计时。完成的标准是所有已解析的地址共享一个总截止时间，从而使端点尝试保持在文档所述的超时范围内。

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