Use language settings' prettier parsers as a fallback for files with no path (#12273)

Follow-up of
https://github.com/zed-industries/zed/pull/12095#issuecomment-2123230762
reverting back part of https://github.com/zed-industries/zed/pull/11558
that was related to `language.toml` parsing.

Now all extensions that define `prettier_parser_name` in their language
configs, will enable formatting untitled buffers without any extra
language settings like

```json
{
  "languages": {
    "JSON": {
      "prettier": {
        "allowed": true,
        "parser": "json"
      }
    }
  }
}
```



Release Notes:

- Improved ergonomics of untitled buffer formatting with prettier, no
extra language settings are needed by default.

crates/languages/src/tsx/config.toml

@@ -15,6 +15,7 @@ brackets = [
 ]
 word_characters = ["#", "$"]
 scope_opt_in_language_servers = ["tailwindcss-language-server", "emmet-language-server"]
+prettier_parser_name = "typescript"
 tab_size = 2
 
 [overrides.element]