CI: Upgrade Ubuntu runners from v22.04 to v24.04 (#2064)

CI: Upgrade Ubuntu runners from v22.04 to v24.04 (#2064)

* Ubuntu 24.04 uses different apt sources file location and format.

* Some Ubuntu 24.04 GitHub Actions runners lack libltdl-dev as detailed
  at https://github.com/actions/runner-images/issues/11316.
  We could explicitly install libltdl-dev for functionality tests, but
  decided to go one step further and unify all prerequisites
  installation steps for tests that build Squid on Ubuntu.

Also added a hack to fix /etc/hosts broken on some Ubuntu runners and
resulting in Squid startup errors during functionality tests:

    kid1| ERROR: ipcacheAddEntryFromHosts: Bad IP address '-e'