url: update IDNA error conditions

This commit contains three separate changes:

- Always return a string from ToUnicode no matter if an error occurred.
- Disable CheckHyphens boolean flag. This flag will soon be enabled in
  the URL Standard, but is implemented manually by selectively ignoring
  certain errors.
- Enable CheckBidi boolean flag per URL Standard update.

This allows domain names with hyphens at 3 and 4th position, as well as
those with leading and trailing hyphens. They are technically invalid,
but seen in the wild.

Tests are updated and simplified accordingly.

PR-URL: https://github.com/nodejs/node/pull/12966
Fixes: https://github.com/nodejs/node/issues/12965
Refs: https://github.com/whatwg/url/pull/309


Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>