Improvements to the integration/system test environment

[mozzieongit]

• Try out sudo ip a add 127.0.0.2/8 dev lo with --container-options --cap-add=NET_ADMIN to enable AXFRs to NSD and BIND.
• Add environment variables with IPs and ports for use in tests, so that
  • (1) seeing them does not require knowledge about which service is running where (and scripts/test can use the variables instead), and
  • (2) changing the service's IPs doesn't involve updating all tests.
• Maybe set up a machine to run the tests on (act can be run on a remote docker host: https://nektosact.com/usage/custom_engine.html#using-act-with-remote-docker-engine-via-ssh)
• Try out actions-rust-lang/setup-rust-toolchain@v1 to enable testing with different rust versions (hecrj/setup-rust-action@v2 was broken in act)