fix: invert reuseport feature

[keepsimple1]

Address issue #428 .

Problem:

The reuseport feature added in #414 introduced a backward compatibility issue.

Users who depend on this crate with default_features = false would silently lose the SO_REUSEPORT socket option. This could cause socket bind failures on systems where SO_REUSEPORT is required for multicast port sharing (e.g., macOS/BSD).

Fix:

This PR inverts the feature to no_reuseport: instead of opting in to SO_REUSEPORT via a default feature, users on old kernels opt out by enabling no_reuseport. This ensures default_features = false users retain the same behavior as before #414.
This PR removes the feature reuseport. When set_reuseport fails, we log it and move on. If this causes any other problems, we will catch them down the road (very quickly I think).

Migration

If you need to disable SO_REUSEPORT (e.g., old Linux kernels before 3.9): use features = ["no_reuseport"].. Remove the use of the feature, and it will be handled.