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/benchmark/catch_benchmark.hpp

@@ -19,7 +19,7 @@
 #include <catch2/interfaces/catch_interfaces_capture.hpp>
 #include <catch2/interfaces/catch_interfaces_config.hpp>
 #include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
-#include <catch2/interfaces/catch_interfaces_reporter.hpp>
+#include <catch2/benchmark/detail/catch_benchmark_stats.hpp>
 #include <catch2/benchmark/catch_clock.hpp>
 #include <catch2/benchmark/catch_environment.hpp>
 #include <catch2/benchmark/catch_execution_plan.hpp>

src/catch2/benchmark/catch_benchmark_all.hpp

@@ -33,6 +33,8 @@
 #include <catch2/benchmark/catch_sample_analysis.hpp>
 #include <catch2/benchmark/detail/catch_analyse.hpp>
 #include <catch2/benchmark/detail/catch_benchmark_function.hpp>
+#include <catch2/benchmark/detail/catch_benchmark_stats.hpp>
+#include <catch2/benchmark/detail/catch_benchmark_stats_fwd.hpp>
 #include <catch2/benchmark/detail/catch_complete_invoke.hpp>
 #include <catch2/benchmark/detail/catch_estimate_clock.hpp>
 #include <catch2/benchmark/detail/catch_measure.hpp>

src/catch2/benchmark/detail/catch_benchmark_stats.hpp

@@ -0,0 +1,64 @@
+
+//              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_BENCHMARK_STATS_HPP_INCLUDED
+#define CATCH_BENCHMARK_STATS_HPP_INCLUDED
+
+#include <catch2/internal/catch_move_and_forward.hpp>
+#include <catch2/benchmark/catch_estimate.hpp>
+#include <catch2/benchmark/catch_outlier_classification.hpp>
+// The fwd decl & default specialization needs to be seen by VS2017 before
+// BenchmarkStats itself, or VS2017 will report compilation error.
+#include <catch2/benchmark/detail/catch_benchmark_stats_fwd.hpp>
+
+#include <string>
+#include <vector>
+
+namespace Catch {
+
+    struct BenchmarkInfo {
+        std::string name;
+        double estimatedDuration;
+        int iterations;
+        unsigned int samples;
+        unsigned int resamples;
+        double clockResolution;
+        double clockCost;
+    };
+
+    template <class Duration>
+    struct BenchmarkStats {
+        BenchmarkInfo info;
+
+        std::vector<Duration> samples;
+        Benchmark::Estimate<Duration> mean;
+        Benchmark::Estimate<Duration> standardDeviation;
+        Benchmark::OutlierClassification outliers;
+        double outlierVariance;
+
+        template <typename Duration2>
+        operator BenchmarkStats<Duration2>() const {
+            std::vector<Duration2> samples2;
+            samples2.reserve(samples.size());
+            for (auto const& sample : samples) {
+                samples2.push_back(Duration2(sample));
+            }
+            return {
+                info,
+                CATCH_MOVE(samples2),
+                mean,
+                standardDeviation,
+                outliers,
+                outlierVariance,
+            };
+        }
+    };
+
+
+} // end namespace Catch
+
+#endif // CATCH_BENCHMARK_STATS_HPP_INCLUDED

src/catch2/benchmark/detail/catch_benchmark_stats_fwd.hpp

@@ -0,0 +1,23 @@
+
+//              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_BENCHMARK_STATS_FWD_HPP_INCLUDED
+#define CATCH_BENCHMARK_STATS_FWD_HPP_INCLUDED
+
+#include <chrono>
+
+namespace Catch {
+
+    // We cannot forward declare the type with default template argument
+    // multiple times, so it is split out into a separate header so that
+    // we can prevent multiple declarations in dependees
+    template <typename Duration = std::chrono::duration<double, std::nano>>
+    struct BenchmarkStats;
+
+} // end namespace Catch
+
+#endif // CATCH_BENCHMARK_STATS_FWD_HPP_INCLUDED