adoptopenjdk-icedtea-web: rename from icedtea_web

This is a follow up of https://github.com/NixOS/nixpkgs/pull/66422

- rename icedtea_web to adoptopenjdk-icedtea-web to reflect the new governance
- add icedtea_web and icedtea8_web to aliases.nix for backwards compatibility
- update the attribute name where icedtea_web is used