Add a new reporter customization point: reporting all assertions

By opting the JUnit and XML reporters into it, we no longer run
into problem where they underreport the results without `-s` flag.

Related to #1264, #1267, #1310

include/internal/catch_interfaces_reporter.h

@@ -42,6 +42,7 @@ namespace Catch {
 
     struct ReporterPreferences {
         bool shouldRedirectStdOut = false;
+        bool shouldReportAllAssertions = false;
     };
 
     template<typename T>