uvloop is broken for abstract sockets - create_unix_connection does not work for abstract sockets as libuv does not support them

* **uvloop version**: master
* **Python version**: 3.10+
* **Platform**: unix
* **Can you reproduce the bug with `PYTHONASYNCIODEBUG` in env?**: yes
* **Does uvloop behave differently from vanilla asyncio? How?**: yes

uvloop:
tr = UnixTransport.new(self, protocol, None, waiter, context)
tr.connect(path) <--- uses uv_pipe_connect which uses uv__strscpy which assumes zero terminated string

asyncio:
sock_connect -> getsockaddrarg (in socketmodule.c) which uses memcpy


I have raised this with libuv as issue: https://github.com/libuv/libuv/discussions/3911

Start at create_unix_connection and the shown UnixTransport.new/tr.connect(path) path, then compare it with vanilla asyncio's socket_connect handling. Read the linked libuv discussion about abstract sockets before deciding whether the fix belongs in uvloop or libuv. Done means abstract Unix socket connections work as expected, with the behavior verified against asyncio.

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