Add basic tcp socket test

crates/lb/tests/net.lua

@@ -0,0 +1,17 @@
+local ok, net = pcall(require, "lb:net")
+if not ok then return end
+
+describe("tcp", function()
+  describe("socket", function()
+    test("bind", function()
+      local socket = net:bind_tcp("127.0.0.1")
+
+      -- binds to the correct port
+      assert(tostring(socket:local_addr():ip()) == "127.0.0.1")
+      assert(socket:local_addr():port() ~= 0)
+
+      -- should not be able to rebind socket
+      assert(not pcall(socket.bind, socket, net:socketaddr("127.0.0.1")))
+    end)
+  end)
+end)