VideoCommon: fix graphics target texture names for efb/xfb

[iwubcode]

The efb/xfb names were not being calculated properly when defining actions that used them as textures. This made it impossible to write mods to skip (or technically move/scale) these draw calls.

I found this when trying to make a bloom replacement shader mod for Arc Rise Fantasia using the pp PR. I was removing bloom and applying the new bloom shader but a corner of the screen was unbloomed. Turns out the game was drawing in the corner to try and write over the place where it drew the bloom EFB copy. When I tried to get rid of that draw and I couldn't, I found this bug :)

[AdmiralCurtiss]

I think you need to check the result of texture_info.find_first_of("_", letter_n_pos) against npos for the case where there's no _ after the n.

[iwubcode]

@AdmiralCurtiss - it does work: https://godbolt.org/z/8MEh3TbE4

Though admittedly that's likely because npos is a very large value which means we will always erase wherever n is at. Still worth changing?

[AdmiralCurtiss]

Yes, it feels a bit magic otherwise.

You also have a bug in here if the string starts with n : https://godbolt.org/z/PMoPWxfG1

[AdmiralCurtiss]

A mid-string n not preceded by a _ is also not handled correctly...

[iwubcode]

Alright, I'll fix those up. Thanks for looking it over!

[iwubcode]

@AdmiralCurtiss - what do you think now?

I'm not sure why there is a FifoCI change..

[AdmiralCurtiss]

I don't understand why you're checking for the prefix in the middle of the string and then rejecting the result if it's not at the start. Is there any reason to explicitly reject texture filenames that happen to have efb1 in the middle of their name? (a valid hexadecimal chain of characters, too!) Why not just do:

  const auto handle_fb_texture =
      [&texture_info](std::string_view type) -> std::optional<std::string> {
    const auto letter_n_pos = texture_info.find("_n");
    if (letter_n_pos == std::string::npos)
    {
      ERROR_LOG_FMT(VIDEO,
                    "Failed to load mod configuration file, value in 'texture_filename' "
                    "is {} without a count",
                    type);
      return std::nullopt;
    }

    const auto post_underscore = texture_info.find_first_of("_", letter_n_pos + 2);
    if (post_underscore == std::string::npos)
      return texture_info.erase(letter_n_pos, texture_info.size() - letter_n_pos);
    else
      return texture_info.erase(letter_n_pos, post_underscore - letter_n_pos);
  };

  if (texture_info.starts_with(EFB_DUMP_PREFIX))
    return handle_fb_texture("an efb");
  else if (texture_info.starts_with(XFB_DUMP_PREFIX))
    return handle_fb_texture("a xfb");
  return texture_info;

[iwubcode]

@AdmiralCurtiss - no real reason. I've been very reactionary to your requests instead of taking a step back and re-looking at the algorithm. The use of find("_n") is a smarter move. And I didn't have c++20 originally. Good stuff. From what I can tell, this handles all the scenarios.

Do note, that these don't support hashes (at least at the moment). They are size + format only. Still this is very clean. A little tempted to reject any that don't begin with efb,xfb, or tex1 but eh. Probably unnecessary. I've pushed it up.