[reflection][feat]Add index of

[qicosmos]

Why

add new index_of interface.

What is changing

Example

struct simple {
  int color;
  int id;
  std::string str;
  int age;
};

  auto i = index_of(&simple::id);
  CHECK(i == 1);
  i = index_of(&simple::age);
  CHECK(i == 3);

[github-actions]

for detail, goto summary download Artifacts base-ylt-cov-report(base commit coverage report) and ylt-cov-report(current pull request coverage report)