THRIFT-5930: c_glib: reject oversized Unix socket paths in thrift_server_socket_listen()

[neosys007]

This PR fixes the server-side Unix socket path copy in the C GLib transport.

In current head, thrift_server_socket_listen() builds a stack sockaddr_un and copies tsocket->path into sun_path with strlen(path) + 1. That only works when the configured path is shorter than the destination buffer; otherwise the copy can run past the end of the local sockaddr_un before bind() is even called.

The fix is intentionally small:

• check the path length against sizeof(struct sockaddr_un.sun_path) first,
• return a transport error if the path does not fit,
• keep the rest of the server-side behavior unchanged.

I also added regression coverage in lib/c_glib/test/testtransportsocket.c that checks the server listen path rejects an overlong Unix socket path cleanly.

Validation performed locally:

• git diff --check
• syntax-only compile for the changed C files
• the C GLib transport sources compile cleanly apart from existing OpenSSL deprecation warnings unrelated to this change.

Related Jira:

• https://issues.apache.org/jira/browse/THRIFT-5930

[Jens-G]

strncpy()?

[neosys007]

You are right to call this out, but this file should not be part of THRIFT-5930 in the first place. This PR branch accidentally pulled in the separate saferealpath change from THRIFT-5932. I will clean up #3354 so it only contains the c_glib server-socket changes.