Handle active Sections for fatal errors

Closes catchorg#1210

When a signal is caught, the destructors of Sections will not be called.
Thus, we must call `sectionEndedEarly` manually for those Sections.

Example test case:
```
TEST_CASE("broken") {
   SECTION("section") {
      /// Use illegal cpu instruction
      __asm__ __volatile__("ud2" : : : "memory");
   }
}
```

src/catch2/internal/catch_run_context.cpp

@@ -450,6 +450,13 @@ namespace Catch {
         assertionEnded(CATCH_MOVE(result) );
         resetAssertionInfo();
 
+        // Best effort cleanup for sections that have not been destructed yet
+        // Since this is a fatal error, we have not had and won't have the opportunity to destruct them properly
+        while (!m_activeSections.empty()) {
+            auto nl = m_activeSections.back()->nameAndLocation();
+            SectionEndInfo endInfo{ SectionInfo(CATCH_MOVE(nl.location), CATCH_MOVE(nl.name)), {}, 0.0 };
+            sectionEndedEarly(CATCH_MOVE(endInfo));
+        }
         handleUnfinishedSections();
 
         // Recreate section for test case (as we will lose the one that was in scope)