Add Kernel API for subscribe broadcast message by SSE

[Zuoqiu-Yingyi]

REL: #9031

当前广播消息监听 API /ws/broadcast 每次仅能订阅一个信道

新增内核 API /es/broadcast/subscribe，用户可以使用 EventSource 同时订阅多个广播信道
The new kernel API /es/broadcast/subscribe allows users use EventSource to subscribe multiple broadcast channels at the same time

使用示例 | Examples:

// 订阅所有广播信道 | Subscribe to all broadcast channels
const es = new EventSource("/es/broadcast/subscribe");
es.addEventListener("channel-name", (e) => {
  console.log(e);
});

// 仅订阅广播信道 "ch1" | Subscribe to channel "ch1"
const es1 = new EventSource("/es/broadcast/subscribe?channel=ch1");
es1.addEventListener("ch1", (e) => {
  console.log(e);
});

// 同时订阅广播信道 "ch1" 与 "ch2" | Subscribe to channel "ch1" and "ch2"
const es12 = new EventSource("/es/broadcast/subscribe?channel=ch1&channel=ch2");
es12.addEventListener("ch1", (e) => {
  console.log(e);
});
es12.addEventListener("ch2", (e) => {
  console.log(e);
});

// 自定义连接断开后自动重连时间间隔 (单位: ms) | Custom automatic reconnection interval after disconnection (unit: ms)
const es_retry = new EventSource("/es/broadcast/subscribe?retry=1000");

数据格式 | Data format:

• 字符串消息 | string message: abc -> abc
  • 原格式
    raw
• 二进制消息 | binary message: abc -> "YWJj"
  • 使用双引号 " 包裹的 Base64 编码字符串
    A Base64-encoded string wrapped in quotation marks "

已测试 | Tested

[88250]

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