Wasm backend doesn't support C++ exceptions

Currently, all C++ code needs to be compiled with -fno-exceptions when using the wasm backend, so C++ exceptions is not supported at all. This is not our fault though; the wasm exception handling proposal is not supported by wasmtime yet, and wasi-sdk doesn't enable exceptions in its sysroot build. This ticket is meant to track test cases that do make use of C++ exceptions (T11829).