abseil-cleanup-ctad

Suggests switching the initialization pattern of absl::Cleanup instances from the factory function to class template argument deduction (CTAD), in C++17 and higher.

auto c1 = absl::MakeCleanup([] {});

const auto c2 = absl::MakeCleanup(std::function<void()>([] {}));

becomes

absl::Cleanup c1 = [] {};

const absl::Cleanup c2 = std::function<void()>([] {});