Unit test with Julienne

[rouson]

Because the Veggies unit testing framework exposes what appears to be an internal compiler error in LLVM Flang (flang-new), this PR refactors the Caffeine test suite to replace Veggies with Julienne, which provides similar functionality and supports Flang. This commit also removes the unused iso_varying_string dependency and renames all test/caf_* files to test/prif_*.

To Do

• [x] Update fpm.toml.template: replace veggies with julienne and remove the unused iso_varying_string dependency
• [x] Replace main test program
• [x] Refactor/rename prif_init test module
• [x] Refactor/rename prif_allocate test module
• [x] Refactor/rename prif_co_broadcast test module
• [x] Refactor/rename prif_co_max test module
• [x] Refactor/rename prif_co_min test module
• [x] Refactor/rename prif_co_reduce test module
• [x] Refactor/rename prif_co_sum test module
• [x] Refactor/rename prif_error_stop test module
• [x] Refactor/rename prif_image_index test module
• [x] Refactor/rename prif_num_images test module
• [x] Refactor/rename prif_rma test module
• [x] Refactor/rename prif_stop test module
• [x] Refactor/rename prif_teams test module
• [x] Refactor/rename prif_this_image test module