Refactor file icons to use IconTheme (#23153)

This PR adds the initial concept of an `IconTheme` and refactors
`FileIcons` to use it to resolve the icons.

The `IconTheme` will ultimately be used to allow users to select a
different set of icons to use. Currently, however, this is just laying
the foundation for that work.

The association between file types and icons is now handled by the icon
theme when we resolve file icons. This mapping has been moved out of
`file_types.json` and into `icon_theme.rs`.

Release Notes:

- N/A

assets/icons/file_icons/file_types.json

@@ -210,208 +210,5 @@
     "zsh_profile": "terminal",
     "zshenv": "terminal",
     "zshrc": "terminal"
-  },
-  "types": {
-    "astro": {
-      "icon": "icons/file_icons/astro.svg"
-    },
-    "audio": {
-      "icon": "icons/file_icons/audio.svg"
-    },
-    "bun": {
-      "icon": "icons/file_icons/bun.svg"
-    },
-    "c": {
-      "icon": "icons/file_icons/c.svg"
-    },
-    "code": {
-      "icon": "icons/file_icons/code.svg"
-    },
-    "coffeescript": {
-      "icon": "icons/file_icons/coffeescript.svg"
-    },
-    "collapsed_chevron": {
-      "icon": "icons/file_icons/chevron_right.svg"
-    },
-    "collapsed_folder": {
-      "icon": "icons/file_icons/folder.svg"
-    },
-    "cpp": {
-      "icon": "icons/file_icons/cpp.svg"
-    },
-    "css": {
-      "icon": "icons/file_icons/css.svg"
-    },
-    "dart": {
-      "icon": "icons/file_icons/dart.svg"
-    },
-    "default": {
-      "icon": "icons/file_icons/file.svg"
-    },
-    "diff": {
-      "icon": "icons/file_icons/diff.svg"
-    },
-    "docker": {
-      "icon": "icons/file_icons/docker.svg"
-    },
-    "document": {
-      "icon": "icons/file_icons/book.svg"
-    },
-    "elixir": {
-      "icon": "icons/file_icons/elixir.svg"
-    },
-    "elm": {
-      "icon": "icons/file_icons/elm.svg"
-    },
-    "erlang": {
-      "icon": "icons/file_icons/erlang.svg"
-    },
-    "eslint": {
-      "icon": "icons/file_icons/eslint.svg"
-    },
-    "expanded_chevron": {
-      "icon": "icons/file_icons/chevron_down.svg"
-    },
-    "expanded_folder": {
-      "icon": "icons/file_icons/folder_open.svg"
-    },
-    "font": {
-      "icon": "icons/file_icons/font.svg"
-    },
-    "fsharp": {
-      "icon": "icons/file_icons/fsharp.svg"
-    },
-    "gleam": {
-      "icon": "icons/file_icons/gleam.svg"
-    },
-    "go": {
-      "icon": "icons/file_icons/go.svg"
-    },
-    "graphql": {
-      "icon": "icons/file_icons/graphql.svg"
-    },
-    "haskell": {
-      "icon": "icons/file_icons/haskell.svg"
-    },
-    "hcl": {
-      "icon": "icons/file_icons/hcl.svg"
-    },
-    "heroku": {
-      "icon": "icons/file_icons/heroku.svg"
-    },
-    "image": {
-      "icon": "icons/file_icons/image.svg"
-    },
-    "java": {
-      "icon": "icons/file_icons/java.svg"
-    },
-    "javascript": {
-      "icon": "icons/file_icons/javascript.svg"
-    },
-    "julia": {
-      "icon": "icons/file_icons/julia.svg"
-    },
-    "kotlin": {
-      "icon": "icons/file_icons/kotlin.svg"
-    },
-    "lock": {
-      "icon": "icons/file_icons/lock.svg"
-    },
-    "log": {
-      "icon": "icons/file_icons/info.svg"
-    },
-    "lua": {
-      "icon": "icons/file_icons/lua.svg"
-    },
-    "metal": {
-      "icon": "icons/file_icons/metal.svg"
-    },
-    "nim": {
-      "icon": "icons/file_icons/nim.svg"
-    },
-    "nix": {
-      "icon": "icons/file_icons/nix.svg"
-    },
-    "ocaml": {
-      "icon": "icons/file_icons/ocaml.svg"
-    },
-    "phoenix": {
-      "icon": "icons/file_icons/phoenix.svg"
-    },
-    "php": {
-      "icon": "icons/file_icons/php.svg"
-    },
-    "prettier": {
-      "icon": "icons/file_icons/prettier.svg"
-    },
-    "prisma": {
-      "icon": "icons/file_icons/prisma.svg"
-    },
-    "python": {
-      "icon": "icons/file_icons/python.svg"
-    },
-    "r": {
-      "icon": "icons/file_icons/r.svg"
-    },
-    "react": {
-      "icon": "icons/file_icons/react.svg"
-    },
-    "roc": {
-      "icon": "icons/file_icons/roc.svg"
-    },
-    "ruby": {
-      "icon": "icons/file_icons/ruby.svg"
-    },
-    "rust": {
-      "icon": "icons/file_icons/rust.svg"
-    },
-    "sass": {
-      "icon": "icons/file_icons/sass.svg"
-    },
-    "scala": {
-      "icon": "icons/file_icons/scala.svg"
-    },
-    "settings": {
-      "icon": "icons/file_icons/settings.svg"
-    },
-    "storage": {
-      "icon": "icons/file_icons/database.svg"
-    },
-    "swift": {
-      "icon": "icons/file_icons/swift.svg"
-    },
-    "tcl": {
-      "icon": "icons/file_icons/tcl.svg"
-    },
-    "template": {
-      "icon": "icons/file_icons/html.svg"
-    },
-    "terminal": {
-      "icon": "icons/file_icons/terminal.svg"
-    },
-    "terraform": {
-      "icon": "icons/file_icons/terraform.svg"
-    },
-    "toml": {
-      "icon": "icons/file_icons/toml.svg"
-    },
-    "typescript": {
-      "icon": "icons/file_icons/typescript.svg"
-    },
-    "v": {
-      "icon": "icons/file_icons/v.svg"
-    },
-    "vcs": {
-      "icon": "icons/file_icons/git.svg"
-    },
-    "video": {
-      "icon": "icons/file_icons/video.svg"
-    },
-    "vue": {
-      "icon": "icons/file_icons/vue.svg"
-    },
-    "zig": {
-      "icon": "icons/file_icons/zig.svg"
-    }
   }
 }