Merge bitcoin/bitcoin#25426: net: add new method Sock::GetSockName() that wraps getsockname() and use it in GetBindAddress()

a8d6abba5e net: change GetBindAddress() to take Sock argument (Vasil Dimov)
748dbcd9f2 net: add new method Sock::GetSockName() that wraps getsockname() (Vasil Dimov)

Pull request description:

  _This is a piece of #21878, chopped off to ease review._

  Wrap the syscall `getsockname()` in `Sock::GetSockName()` and change `GetBindAddress()` to take a `Sock` argument so that it can use the wrapper.

  This further encapsulates syscalls inside the `Sock` class and makes the callers mockable.

ACKs for top commit:
  laanwj:
    Code review ACK a8d6abba5e

Tree-SHA512: 3a73463258c0057487fb3fd67215816b03a1c5160f45e45930eaeef86bb3611ec385794cdb08339aa074feba8ad67cd2bfd3836f6cbd40834e15d933214a05dc

src/test/util/net.h

@@ -147,6 +147,12 @@ public:
 
     int SetSockOpt(int, int, const void*, socklen_t) const override { return 0; }
 
+    int GetSockName(sockaddr* name, socklen_t* name_len) const override
+    {
+        std::memset(name, 0x0, *name_len);
+        return 0;
+    }
+
     bool Wait(std::chrono::milliseconds timeout,
               Event requested,
               Event* occurred = nullptr) const override