Session::open does not fail over when openSession/requestStatementId fails (only TCP-layer failover)

`Session::open` only fails over at the TCP layer: the loop over `config.endpoints` opens a `Connection`, but `authenticate()` (openSession + requestStatementId) runs **after** the loop. `reconnect()` does the opposite — it retries connect **and** authenticate for every endpoint.

With a 3-node cluster where one node accepts TCP but fails `openSession` (e.g. overloaded, misconfigured, or wedged by the missing socket timeout), roughly one `open()` in three fails while 2 of 3 nodes are healthy.

Fix: move the `authenticate()` step inside the endpoint loop, mirroring `reconnect()`.

从 Session::open 开始，将其端点循环与 reconnect() 进行比较。跟踪 authenticate()，包括 openSession 和 requestStatementId，以了解每个失败在哪里得到处理。完成的标准是：身份验证失败会导致尝试下一个已配置的端点，与 reconnect() 的行为一致；issue 中未指定任何测试文件。

由索引模型根据 Issue 内容生成。