Merge #268: Use throwRecoverableException instead of raw throw for stored exceptions

23be44b Use throwRecoverableException instead of raw throw for stored exceptions (Alfonso Roman Zubeldia)

Pull request description:

  Replace `throw kj::mv(*exception)` with `kj::throwRecoverableException(kj::mv(*exception))` in the async worker thread exception handler in `type-context.h`.

  A raw throw creates a `kj::Exception` with the calling binary's typeinfo. On macOS with `-fvisibility=hidden`, this typeinfo is not coalesced with `libkj.dylib`'s copy by the dynamic linker, so `getCaughtExceptionAsKj()`'s `catch (kj::Exception& e)` fails and falls through to `catch (...)`, producing `unknown non-KJ exception of type: kj::Exception` errors.

  `throwFatalException()` routes the throw through libkj, wrapping it in `ExceptionImpl` with consistent typeinfo. This matches the pattern KJ uses internally in `kj/async-inl.h` when re-throwing stored exceptions from promises.

  Context: bitcoin/bitcoin#34723, bitcoin/bitcoin#35014

ACKs for top commit:
  Sjors:
    ACK 23be44b
  ryanofsky:
    Code review ACK 23be44b. Thanks for the fix!

Tree-SHA512: b23e43b188255e76c499376f30e09db0868ab0dcc7fa4bd0b0f1ed38ab719d1c0a5e4a6cf7e2eb598a55ebdd0c28dda50623bdbf003ff56c3b6483ba1db916ee

Author: ryanofsky

include/mp/type-context.h

@@ -189,7 +189,7 @@ auto PassField(Priority<1>, TypeList<>, ServerContext& server_context, const Fn&
             }
         })) {
             MP_LOG(loop, Log::Error) << "IPC server request #" << req << " uncaught exception (" << kj::str(*exception).cStr() << ")";
-            throw kj::mv(*exception);
+            kj::throwRecoverableException(kj::mv(*exception));
         }
         return call_context;
         // End of scope: if KJ_DEFER was reached, it runs here