Make ListeningReporter final

In general, for Catch2 v3 we are making virtual types `final`,
unless they were explicitly designed to be derived-from.
`ListeningReporter` is definitely not designed to be derived-from.

docs/release-notes.md

@@ -56,11 +56,16 @@
 * Lvalues of composed matchers cannot be composed further
 * Uses of `REGISTER_TEST_CASE` macro need to be followed by a semicolon
   * This does not change `TEST_CASE` and friends in any way
+* `IStreamingReporter::IsMulti` member function was removed
+  * This is _very_ unlikely to actually affect anyone, as it was default-implemented in the interface, and only used internally
+* `ListeningReporter` is now final
+
 
 ### Fixes
 * The `INFO` macro no longer contains superfluous semicolon (#1456)
 * The `--list*` family of command line flags now return 0 on success (#1410, #1146)
 
+
 ### Other changes
 * `CATCH_CONFIG_DISABLE_MATCHERS` no longer exists.
   * If you do not want to use Matchers in a TU, do not include their header.

src/catch2/catch_interfaces_reporter.cpp

@@ -112,7 +112,6 @@ namespace Catch {
     TestRunStats::~TestRunStats() = default;
 
     void IStreamingReporter::fatalErrorEncountered( StringRef ) {}
-    bool IStreamingReporter::isMulti() const { return false; }
 
     void IStreamingReporter::listReporters(std::vector<ReporterDescription> const& descriptions, Config const& config) {
         Catch::cout() << "Available reporters:\n";

src/catch2/catch_interfaces_reporter.h

@@ -241,8 +241,6 @@ namespace Catch {
         // Default empty implementation provided
         virtual void fatalErrorEncountered( StringRef name );
 
-        virtual bool isMulti() const;
-
         // Listing support
         virtual void listReporters(std::vector<ReporterDescription> const& descriptions, Config const& config);
         virtual void listTests(std::vector<TestCaseHandle> const& tests, Config const& config);

src/catch2/reporters/catch_reporter_listening.cpp

@@ -150,10 +150,6 @@ namespace Catch {
         m_reporter->skipTest( testInfo );
     }
 
-    bool ListeningReporter::isMulti() const {
-        return true;
-    }
-
     void ListeningReporter::listReporters(std::vector<ReporterDescription> const& descriptions, Config const& config) {
         for (auto const& listener : m_listeners) {
             listener->listReporters(descriptions, config);

src/catch2/reporters/catch_reporter_listening.h

@@ -11,7 +11,7 @@
 
 namespace Catch {
 
-    class ListeningReporter : public IStreamingReporter {
+    class ListeningReporter final : public IStreamingReporter {
         using Reporters = std::vector<IStreamingReporterPtr>;
         Reporters m_listeners;
         IStreamingReporterPtr m_reporter = nullptr;
@@ -50,7 +50,6 @@ namespace Catch {
         void testRunEnded( TestRunStats const& testRunStats ) override;
 
         void skipTest( TestCaseInfo const& testInfo ) override;
-        bool isMulti() const override;
 
         void listReporters(std::vector<ReporterDescription> const& descriptions, Config const& config) override;
         void listTests(std::vector<TestCaseHandle> const& tests, Config const& config) override;