message: Enable multi-threading in qsim Accelerator by default
diff: #include "IRUtils.hpp"
  #include <cassert>
  #include <optional>
  +#include <thread>
  namespace {
  inline bool isMeasureGate(const xacc::InstPtr &in_instr) {
  return (in_instr->name() == "Measure");
  @@ -99,7 +100,8 @@ namespace xacc {
  namespace quantum {
  void QsimAccelerator::initialize(const HeterogeneousMap &params) {
  m_qsimParam.seed = 1;
  - m_numThreads = 1;
  + m_numThreads =
  + std::max(1, static_cast<int>(std::thread::hardware_concurrency()));
  m_qsimParam.verbosity = xacc::verbose ? 1 : 0;
  m_shots = -1;
  if (params.keyExists<int>("shots")) {
  