Update '-list' option (#2457)

'-list' option is used to print all sub-tests. But some test do not
support it at all. And all test do not display it the same way, making
it quite complicated for external tools to extract them.

That CL clean the usage so that tests:
- Print the sub-tests list with either '-list' (to prevent breaking
legacy usage) or '--list' (to match other options)
- Do not print anything else when the option is used

test_conformance/conversions/test_conversions.cpp

@@ -112,6 +112,35 @@ int main(int argc, const char **argv)
     int error;
 
     argc = parseCustomParam(argc, argv);
+    if (gListTests)
+    {
+        for (unsigned dst = 0; dst < kTypeCount; dst++)
+        {
+            for (unsigned src = 0; src < kTypeCount; src++)
+            {
+                for (unsigned sat = 0; sat < 2; sat++)
+                {
+                    // skip illegal saturated conversions to float type
+                    if (gSaturationNames[sat] == std::string("_sat")
+                        && (gTypeNames[dst] == std::string("float")
+                            || gTypeNames[dst] == std::string("half")
+                            || gTypeNames[dst] == std::string("double")))
+                    {
+                        continue;
+                    }
+                    for (unsigned rnd = 0; rnd < kRoundingModeCount; rnd++)
+                    {
+                        vlog("\t%s\n",
+                             (std::string(gTypeNames[dst])
+                              + gSaturationNames[sat] + gRoundingModeNames[rnd]
+                              + "_" + gTypeNames[src])
+                                 .c_str());
+                    }
+                }
+            }
+        }
+        return 0;
+    }
     if (argc == -1)
     {
         return 1;