docs: update connector doc for3.0 (#17020)

* docs: update csharp connector status

* docs: fix csharp ws bulk pulling

* docs: clarify database param is optional to websocket dsn

docs/en/14-reference/03-connector/06-rust.mdx

@@ -116,7 +116,7 @@ The parameters are described as follows:
 - **protocol**: Specify which connection method to use. For example, `taos+ws://localhost:6041` uses Websocket to establish connections.
 - **username/password**: Username and password used to create connections.
 - **host/port**: Specifies the server and port to establish a connection. If you do not specify a hostname or port, native connections default to `localhost:6030` and Websocket connections default to `localhost:6041`.
-- **database**: Specify the default database to connect to.
+- **database**: Specify the default database to connect to. It's optional.
 - **params**：Optional parameters.
 
 A sample DSN description string is as follows:

docs/en/14-reference/03-connector/09-csharp.mdx

@@ -151,7 +151,7 @@ The parameters are described as follows:
 * **protocol**: Specify which connection method to use (support http/ws). For example, `ws://localhost:6041` uses Websocket to establish connections. 
 * **username/password**: Username and password used to create connections.
 * **host/port**: Specifies the server and port to establish a connection. Websocket connections default to `localhost:6041`.
-* **database**: Specify the default database to connect to.
+* **database**: Specify the default database to connect to. It's optional.
 * **params**：Optional parameters.
 
 A sample DSN description string is as follows:

docs/zh/08-connector/26-rust.mdx

@@ -116,7 +116,7 @@ DSN 描述字符串基本结构如下：
 - **protocol**: 显示指定以何种方式建立连接，例如：`taos+ws://localhost:6041` 指定以 Websocket 方式建立连接。
 - **username/password**: 用于创建连接的用户名及密码。
 - **host/port**: 指定创建连接的服务器及端口，当不指定服务器地址及端口时（`taos://`），原生连接默认为 `localhost:6030`，Websocket 连接默认为 `localhost:6041` 。
-- **database**: 指定默认连接的数据库名。
+- **database**: 指定默认连接的数据库名，可选参数。
 - **params**：其他可选参数。
 
 一个完整的 DSN 描述字符串示例如下：

docs/zh/08-connector/40-csharp.mdx

@@ -154,7 +154,7 @@ namespace TDengineExample
   
 * **host/port**: 指定创建连接的服务器及端口，WebSocket 连接默认为 `localhost:6041` 。
   
-* **database**: 指定默认连接的数据库名。
+* **database**: 指定默认连接的数据库名，可选参数。
 
 * **params**：其他可选参数。