Introduced ReusableStringStream and removed all uses of std::ostringstream from the main path

ReusableStringStream holds a std::ostringstream internally, but only exposes the ostream interface.
It caches a pool of ostringstreams in a vector which is currently global, but will be made thread-local.

Altogether this should enable both runtime and compile-time benefits. although more work is needed to realise the compile time opportunities.

include/internal/catch_wildcard_pattern.cpp

@@ -9,6 +9,7 @@
 #include "catch_enforce.h"
 #include "catch_string_manip.h"
 
+#include <sstream>
 
 namespace Catch {