[std.socket] Cast assign to getaddrinfoPointer is not @safe

[ntrel]

Fixes needed for dlang/dmd#16315

With that pull, using a type qualifier cast is not @safe to use as an lvalue.
Workaround this with @trusted lambdas. This is not ideal, but the alternative of making the whole softUnittest argument @trusted then might fail to check the other calls are @safe.

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