Cleanup internal includes by splitting out some event structs

* Split out BenchmarkInfo and BenchmarkStats to their own header
* Outline BenchmarkStats<> declaration to separate header
* Split out TestRunInfo into its own header

These changes let us remove the large `interfaces_reporter.hpp`
include from `benchmark.hpp`, and replace it with
`interfaces_capture.hpp` in `run_context.hpp`.

I also cleaned out `interfaces_repoter.hpp` from reporter headers
that depend on `reporter_common_base.hpp`. This will not change
anything in the actual inclusion set, but makes it logically
more consistent.

src/catch2/internal/catch_run_context.cpp

@@ -8,8 +8,9 @@
 #include <catch2/internal/catch_run_context.hpp>
 
 #include <catch2/catch_user_config.hpp>
-#include <catch2/interfaces/catch_interfaces_generatortracker.hpp>
 #include <catch2/interfaces/catch_interfaces_config.hpp>
+#include <catch2/interfaces/catch_interfaces_generatortracker.hpp>
+#include <catch2/interfaces/catch_interfaces_reporter.hpp>
 #include <catch2/internal/catch_compiler_capabilities.hpp>
 #include <catch2/internal/catch_context.hpp>
 #include <catch2/internal/catch_enforce.hpp>

src/catch2/internal/catch_run_context.hpp

@@ -8,8 +8,9 @@
 #ifndef CATCH_RUN_CONTEXT_HPP_INCLUDED
 #define CATCH_RUN_CONTEXT_HPP_INCLUDED
 
-#include <catch2/interfaces/catch_interfaces_reporter.hpp>
+#include <catch2/interfaces/catch_interfaces_capture.hpp>
 #include <catch2/internal/catch_test_registry.hpp>
+#include <catch2/internal/catch_test_run_info.hpp>
 #include <catch2/internal/catch_fatal_condition_handler.hpp>
 #include <catch2/catch_test_case_info.hpp>
 #include <catch2/catch_message.hpp>
@@ -26,6 +27,8 @@ namespace Catch {
 
     class IGeneratorTracker;
     class IConfig;
+    class IEventListener;
+    using IEventListenerPtr = Detail::unique_ptr<IEventListener>;
 
     ///////////////////////////////////////////////////////////////////////////
 

src/catch2/internal/catch_test_run_info.hpp

@@ -0,0 +1,22 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+#ifndef CATCH_TEST_RUN_INFO_HPP_INCLUDED
+#define CATCH_TEST_RUN_INFO_HPP_INCLUDED
+
+#include <catch2/internal/catch_stringref.hpp>
+
+namespace Catch {
+
+    struct TestRunInfo {
+        constexpr TestRunInfo(StringRef _name) : name(_name) {}
+        StringRef name;
+    };
+
+} // end namespace Catch
+
+#endif // CATCH_TEST_RUN_INFO_HPP_INCLUDED