cmake: set HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID on Windows

cmake: set HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID on Windows

`lib/config-win32.h` enables this configuration option unconditionally.
Make it apply to CMake builds as well.

While here, delete a broken check for
`HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID` from `CMakeLists.txt`. This came with
the initial commit [1], but did not include the actual verification code
inside `CMake/CurlTests.c`, so it always failed. A later commit [2]
added a second test, for non-Windows platforms.

Enabling this flag causes test 1056 to fail with CMake builds, as they
do with autotools builds. Let's apply the same solution and ignore the
results here as well.

[1] 4c5307b45655ba75ab066564afdc0c111a8b9291
[2] aec7c5a87c8482b6ddffa352d7d220698652262e

Reviewed-by: Daniel Stenberg
Assisted-by: Marcel Raad
Closes #9726