Add Antithesis intrumentation (#5042)

* Copy Antithesis SDK version 0.4.0 to directory external/
* Add build option `voidstar` to enable instrumentation with Antithesis SDK
* Define instrumentation macros ASSERT and UNREACHABLE in terms of regular C assert
* Replace asserts with named ASSERT or UNREACHABLE
* Add UNREACHABLE to LogicError
* Document instrumentation macros in CONTRIBUTING.md

include/xrpl/basics/scope.h

@@ -20,6 +20,8 @@
 #ifndef RIPPLE_BASICS_SCOPE_H_INCLUDED
 #define RIPPLE_BASICS_SCOPE_H_INCLUDED
 
+#include <xrpl/beast/utility/instrumentation.h>
+
 #include <exception>
 #include <mutex>
 #include <type_traits>
@@ -233,7 +235,9 @@ public:
     explicit scope_unlock(std::unique_lock<Mutex>& lock) noexcept(true)
         : plock(&lock)
     {
-        assert(plock->owns_lock());
+        ASSERT(
+            plock->owns_lock(),
+            "ripple::scope_unlock::scope_unlock : mutex must be locked");
         plock->unlock();
     }