GPU backend

Adds GPU backend and "CUDA" feature to all the tests. As of MR creation, there were no forks in tested IRs so only vanilla non-parallel (single block, single thread) codegen has been tested.

hercules_samples/ccp/Cargo.toml

@@ -4,6 +4,9 @@ version = "0.1.0"
 authors = ["Russel Arbore <rarbore2@illinois.edu>"]
 edition = "2021"
 
+[features]
+cuda = ["juno_build/cuda"]
+
 [build-dependencies]
 juno_build = { path = "../../juno_build" }