Add a string_view variant of base::split_string()

[ckaiser]

Adds a string_view version of base::split_string

Benchmarked difference between the two versions of the function puts the string_view version at around 36-37% faster, although it wasn't extensive testing, just a little microbenchmark:

  auto t0 = std::chrono::high_resolution_clock::now();
  {
    const std::string_view string = "Hello,World";
    for (int i = 0; i < 200000; i++) {
      std::vector<std::string_view> result;
      base::split_string("Hello,World", result, ",");
    }
  }

  auto t1 = std::chrono::high_resolution_clock::now();
  auto view = std::chrono::duration_cast<std::chrono::microseconds>(t1 - t0).count();
  t0 = std::chrono::high_resolution_clock::now();

  {
    const std::string string2 = "Hello,World";
    for (int i = 0; i < 200000; i++) {
      std::vector<std::string> result;
      base::split_string(string2, result, ",");
    }
  }

  t1 = std::chrono::high_resolution_clock::now();
  auto noView = std::chrono::duration_cast<std::chrono::microseconds>(t1 - t0).count();

  std::cout << "string_view: " << view << " us" << std::endl;
  std::cout << "string:      " << noView << " us" << std::endl;

[aseprite-bot]

clang-tidy made some suggestions

[dacap]

Hi @ckaiser, we were avoiding std::string_view at the moment but just for fear of macOS 10.9 incompatibilities. The GitHub CI worked (it compiles with CMAKE_OSX_DEPLOYMENT_TARGET=10.9 for macOS in the same way we compile the official distribution) so it should be safe to start using std::string_view (there are a lot of TODO/places where we use substr() and it'd be nice to use string_views directly).

About base::split_string, just in case there exists base::tok() function (in base/tok.h) which is a little faster and have some kind of different API if required.

The base::tok() function is based on https://github.com/dacap/tok, and there you can find some benchmarks too: https://github.com/dacap/tok/blob/main/benchmarks/tok_benchmarks.cpp
(I'd like to benchmark base::tok() using string_view some time in the future).