message: some helpful ek::Loop log messages
diff: @@ -126,6 +126,8 @@ struct Loop<Mask, enable_if_jit_array_t<Mask>> {
  m_se_offset = jit_side_effects_scheduled(Backend);
  step();
  m_state = 1;
  + jit_log(::LogLevel::Info,
  + "ek::Loop(): --------- begin recording loop ---------");
  }
  }
  @@ -227,8 +229,12 @@ protected:
  m_state++;
  if constexpr (Backend == JitBackend::LLVM)
  m_mask_stack.push(cond.index());
  + jit_log(::LogLevel::Info,
  + "ek::Loop(): ----- recording loop body *again* ------");
  return true;
  } else {
  + jit_log(::LogLevel::Info,
  + "ek::Loop(): --------- done recording loop ----------");
  // No optimization opportunities, stop now.
  for (uint32_t i = 0; i < n; ++i)
  jit_var_dec_ref_ext(m_index_body[i]);
  