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/interfaces/catch_interfaces_capture.hpp

@@ -14,6 +14,7 @@
 #include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_result_type.hpp>
 #include <catch2/internal/catch_unique_ptr.hpp>
+#include <catch2/benchmark/detail/catch_benchmark_stats_fwd.hpp>
 
 namespace Catch {
 
@@ -31,8 +32,6 @@ namespace Catch {
     class IGeneratorTracker;
 
     struct BenchmarkInfo;
-    template <typename Duration = std::chrono::duration<double, std::nano>>
-    struct BenchmarkStats;
 
     namespace Generators {
         class GeneratorUntypedBase;

src/catch2/interfaces/catch_interfaces_reporter.hpp

@@ -13,11 +13,10 @@
 #include <catch2/catch_assertion_result.hpp>
 #include <catch2/internal/catch_message_info.hpp>
 #include <catch2/internal/catch_stringref.hpp>
+#include <catch2/internal/catch_test_run_info.hpp>
 #include <catch2/internal/catch_unique_ptr.hpp>
 #include <catch2/internal/catch_move_and_forward.hpp>
-#include <catch2/benchmark/catch_estimate.hpp>
-#include <catch2/benchmark/catch_outlier_classification.hpp>
-#include <catch2/interfaces/catch_interfaces_capture.hpp>
+#include <catch2/benchmark/detail/catch_benchmark_stats.hpp>
 
 #include <map>
 #include <string>
@@ -57,11 +56,6 @@ namespace Catch {
         std::map<std::string, std::string> m_customOptions;
     };
 
-    struct TestRunInfo {
-        constexpr TestRunInfo(StringRef _name) : name(_name) {}
-        StringRef name;
-    };
-
     struct AssertionStats {
         AssertionStats( AssertionResult const& _assertionResult,
                         std::vector<MessageInfo> const& _infoMessages,
@@ -113,45 +107,6 @@ namespace Catch {
         bool aborting;
     };
 
-
-    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,
-            };
-        }
-    };
-
     //! By setting up its preferences, a reporter can modify Catch2's behaviour
     //! in some regards, e.g. it can request Catch2 to capture writes to
     //! stdout/stderr during test execution, and pass them to the reporter.