--list-* flags write to target specified by the -o flag

Also added tests for the default implementations of list* reporter
helpers.

Closes #2061

src/catch2/interfaces/catch_interfaces_reporter.cpp

@@ -108,20 +108,4 @@ namespace Catch {
 
     void IStreamingReporter::fatalErrorEncountered( StringRef ) {}
 
-    void IStreamingReporter::listReporters(std::vector<ReporterDescription> const& descriptions) {
-        defaultListReporters(
-            Catch::cout(), descriptions, m_config->verbosity() );
-    }
-
-    void IStreamingReporter::listTests(std::vector<TestCaseHandle> const& tests) {
-        defaultListTests( Catch::cout(),
-                          tests,
-                          m_config->hasTestFilters(),
-                          m_config->verbosity() );
-    }
-
-    void IStreamingReporter::listTags(std::vector<TagInfo> const& tags) {
-        defaultListTags( Catch::cout(), tags, m_config->hasTestFilters() );
-    }
-
 } // end namespace Catch

src/catch2/interfaces/catch_interfaces_reporter.hpp

@@ -222,11 +222,11 @@ namespace Catch {
         virtual void fatalErrorEncountered( StringRef name );
 
         //! Writes out information about provided reporters using reporter-specific format
-        virtual void listReporters(std::vector<ReporterDescription> const& descriptions);
+        virtual void listReporters(std::vector<ReporterDescription> const& descriptions) = 0;
         //! Writes out information about provided tests using reporter-specific format
-        virtual void listTests(std::vector<TestCaseHandle> const& tests);
+        virtual void listTests(std::vector<TestCaseHandle> const& tests) = 0;
         //! Writes out information about the provided tags using reporter-specific format
-        virtual void listTags(std::vector<TagInfo> const& tags);
+        virtual void listTags(std::vector<TagInfo> const& tags) = 0;
 
     };
     using IStreamingReporterPtr = Detail::unique_ptr<IStreamingReporter>;