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/protocol/STBitString.h

@@ -170,8 +170,10 @@ template <int Bits>
 void
 STBitString<Bits>::add(Serializer& s) const
 {
-    assert(getFName().isBinary());
-    assert(getFName().fieldType == getSType());
+    ASSERT(getFName().isBinary(), "ripple::STBitString::add : field is binary");
+    ASSERT(
+        getFName().fieldType == getSType(),
+        "ripple::STBitString::add : field type match");
     s.addBitString<Bits>(value_);
 }