Let's adapt this class a bit better to how it's actually being used.
Instead of having valid/invalid states and storing an error in case
it's invalid, a MappedFile is now always valid, and the factory
function that creates it will return an OSError if mapping fails.
If an ELF application contains sections called "serenity_icon_s"
or "serenity_icon_m" then parse these as PNG images and use them
for the 16x16 and 32x32 executable file icons respectively.
If the application is not an ELF binary, the sections do not
exist, the sections are not valid PNGs, or the file cannot be read
then the default application icon will be used.
This is a rather ugly hack just to get app icons to show up in the
FileManager. It would be a lot nicer to embed icons in executables
instead but it's not obvious to me how to do that.
Instead of symlinks showing up with the "filetype-symlink" icon, we now
generate a new icon by taking the target file's icon and slapping a
small arrow emblem on top of it.
This looks rather nice. :^)
This moves file extension to icon mappings from compile time macros to an
INI config file (/etc/FileIconProvider.ini), so file icons can easily be
customized and extended :^)
I also switched the format from a static file extension (".foo") to
glob-like patterns ("*.foo", using StringUtils::matches()), which allows
us to assign icons to specific exactly matching file names, like many
IDEs do - e.g. "CMakeLists.txt" or ".prettierrc".
By using Gfx::Bitmap::is_path_a_supported_image_format() we can
automatically provide the image icon for all supported image formats,
without keeping a second list of image file extensions.
