Do not copy around TestCaseInfo

Now a `TEST_CASE` macro should create a single TestCaseInfo and then
it should never be copied around. This, together with latter changes,
should significantly decrease the number of allocations made before
`main` is even entered.

include/internal/catch_run_context.cpp

@@ -93,7 +93,7 @@ namespace Catch {
         m_reporter->testGroupEnded(TestGroupStats(GroupInfo(testSpec, groupIndex, groupsCount), totals, aborting()));
     }
 
-    Totals RunContext::runTest(TestCase const& testCase) {
+    Totals RunContext::runTest(TestCaseHandle const& testCase) {
         Totals prevTotals = m_totals;
 
         std::string redirectedCout;