test: Add IPv6 inet_pton double "::" test

Unclear but that somehow failed on Windows once (?) according to ticket #33768
but we are not seeing that failure.

Nevertheless, add a simple unit test.

Closes #33768

Signed-off-by: David Goulet <dgoulet@torproject.org>

src/test/test_addr.c

@@ -341,6 +341,7 @@ test_addr_ip6_helpers(void *arg)
   test_pton6_bad("0XYXXY");
   test_pton6_bad("0x");
   test_pton6_bad("0X");
+  test_pton6_bad("2000::1a00::1000:fc098");
 
   /* test internal checking */
   test_external_ip("fbff:ffff::2:7", 0);