Port `python/tests/test_1_online.py::test_gossip_optimization` to Rust

[link2xt]

This legacy Python bindings test seems like a good candidate for porting to Rust, there is no reason for this test to be online.

I noticed this test while working on #6404 because it failed at one point.

[d2weber]

This issue was resolved during the course of 9f5e608. I think this issue can be closed.