[test][prefix] Add two_loops test

This test implements a more complex toolchain
and experiment that will check that loop blocks
are working in more involved setups.
4 jobs for 84_loop_output in 16 minutes and 41 seconds (queued for 7 seconds)
Status Job ID Name Coverage
  Build
passed #169786
docker-build
build_linux_36

00:15:23

64.0%
passed #169787
macosx
build_macosx_36

00:16:37

64.0%
canceled #169553
docker-build
build_linux_36

00:00:04

canceled #169554
macosx
build_macosx_36

00:00:01