- make sure to exclude failing tests when libidn2 is detected by
default.
- ignore test 1560 results. Seen to fail with libidn2.
I'm not sure why this test was not executed earlier:
https://github.com/curl/curl/actions/runs/10354610889/job/28660309355#step:13:3647
- runtests: recognize `libidn2` as a feature.
- move IDN test exclusions from GHA/windows to `tests/data/DISABLED`.
- GHA/windows: drop default `-DUSE_LIBIDN2=ON` cmake config.
Cherry-picked from #14495Closes#14519
