support bind client ip

[wenjiecn]

What problem does this PR solve?

Issue Number: #3157, #3178

Problem Summary:

What is changed and the side effects?

Changed:
1.在ChannelOptions中添加client_host，让用户设置client的ip或hostname
2.在SocketOptions 中添加butil::EndPoint local_side，由 client_host:0 -> local_side
3.在GetNamingServiceThreadOptions添加butil::EndPoint client_end_point，由 client_host:0 -> client_end_point
4.在ComputeChannelSignature中append "clih=client_host", 进行hash
5.在系统调用socket创建socket后，调用bind绑定ip
Side effects:

• Performance effects:

• Breaking backward compatibility:

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Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[wwbmmm]

The unit test is broken, please fix.

[Copilot]

Pull request overview

This PR adds support for binding client sockets to a specific IP address or hostname before connecting to a server, addressing issue #3157. The feature allows users to control which local network interface is used for outgoing connections.

• Adds client_host field to ChannelOptions for user configuration
• Propagates client endpoint information through SocketOptions, GetNamingServiceThreadOptions, and channel signature computation
• Implements socket binding in Socket::Connect() to bind the client socket to the specified IP before connecting

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 12 comments.

Show a summary per file

File	Description
src/brpc/channel.h	Adds client_host string field to ChannelOptions for specifying client IP/hostname
src/brpc/channel.cpp	Implements parsing of client_host to EndPoint and includes it in channel signature; handles both InitSingle and Init paths
src/brpc/socket.h	Adds local_side field to SocketOptions to store the client endpoint
src/brpc/socket.cpp	Implements bind() call in Connect() to bind socket to client IP; initializes local_side from options
src/brpc/socket_map.h	Updates function signatures to accept client_end_point parameter
src/brpc/socket_map.cpp	Passes client_end_point through to SocketOptions when creating sockets
src/brpc/details/naming_service_thread.h	Adds client_end_point field to GetNamingServiceThreadOptions
src/brpc/details/naming_service_thread.cpp	Passes client_end_point to SocketMapInsert when adding servers

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[chenBright]

Please add some unit tests for this feature.