Add an integration test that verifies a list of cases

We need someplace to collect known failures, previous regressions, edge
cases that are difficult to construct from generics, and similar.
Introduce this here.

Author: tgross35

crates/libm-test/src/gen.rs

@@ -1,5 +1,6 @@
 //! Different generators that can create random or systematic bit patterns.
 
+pub mod case_list;
 pub mod edge_cases;
 pub mod random;
 pub mod spaced;