message: Do not print all unregistered parent positions by default
  Summary: Make the output less noisy. It would probably be good to make this tracked somewhere in a follow-up.
diff: #include "DexPosition.h"
  #include "DexUtil.h"
  #include "Show.h"
  +#include "Trace.h"
  DexPosition::DexPosition(uint32_t line) : line(line) {}
  @@ -306,13 +307,16 @@ void RealPositionMapper::write_map_v2() {
  return it->second;
  };
  + size_t unregistered_parent_positions{0};
  +
  for (auto pos : m_positions) {
  uint32_t parent_line = 0;
  try {
  parent_line = pos->parent == nullptr ? 0 : get_line(pos->parent);
  } catch (std::out_of_range& e) {
  - std::cerr << "Parent position " << show(pos->parent) << " of "
  - << show(pos) << " was not registered" << std::endl;
  + ++unregistered_parent_positions;
  + TRACE(OPUT, 1, "Parent position %s of %s was not registered",
  + SHOW(pos->parent), SHOW(pos));
  }
  // of the form "class_name.method_name:(arg_types)return_type"
  const auto& full_method_name = pos->method->str();
  @@ -333,6 +337,13 @@ void RealPositionMapper::write_map_v2() {
  pos_out.write((const char*)&parent_line, sizeof(parent_line));
  }
  + if (unregistered_parent_positions > 0 && !traceEnabled(OPUT, 1)) {
  + TRACE(OPUT, 0,
  + "%zu parent positions had not been registered. Run with TRACE=OPUT:1 "
  + "to list them.",
  + unregistered_parent_positions);
  + }
  +
  std::ofstream ofs(m_filename_v2.c_str(),
  std::ofstream::out | std::ofstream::trunc);
  uint32_t magic = 0xfaceb000; // serves as endianess check
  