Add unit test coverage for conversion to convolution traits (#3515)

Our concept-base conversions are fragile and too complex. We want to refactor to straightforward functions
for each intance trace class template. This change adds unit test coverage to make that refactoring safer.

Author: shumway

experimental/builder/test/CMakeLists.txt

@@ -104,7 +104,8 @@ target_link_libraries(test_ckb_reference_execution PRIVATE utility)
 
 # Tests convolution trait selection and configuration
 add_ck_builder_test(test_ckb_conv_traits
-    conv/ck/test_conv_traits.cpp)
+    conv/ck/test_conv_traits.cpp
+    conv/ck/unit_instance_to_conv_traits.cpp)
 
 # Tests convolution problem description and parameter handling
 add_ck_builder_test(test_ckb_conv_description