Fix bind_interface support guard

[kmehltretter82]

The bind_interface parser guard still checked SO_BINDTODEVICE, but the runtime implementation no longer uses SO_BINDTODEVICE. It uses getifaddrs() on non-Windows/non-AIX platforms instead.

This caused bind_interface to be rejected at config parse time on platforms where the runtime implementation is available, including macOS.

Add a HAVE_BIND_INTERFACE guard and use it consistently for parsing, the ifaddrs include, the bind helper, and the call site. This fixes test/broker/16-config-huge.py on macOS.

Assisted-by: OpenAI Codex (GPT-5)

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Tested with:

• cmake --build build
• env PATH="$PWD/build/test-venv/bin:$PATH" ctest --test-dir build --output-on-failure --parallel 1