feat: new mypyc primitives for weakref.proxy

[BobTheBuidler]

This PR adds 2 new weakref primitives for weakref.proxy (1 and 2 arg)

The C code generates correctly, but I'm not entirely sure why this test is failing. The weakly-proxied object is being destroyed too early, while there should still be a strong reference to it. It also fails if we use the builtin weakref.proxy, so I believe this might be exposing a reference counting bug unrelated to this PR.