Autodetect parser name with prettier by default (#11558)

Closes https://github.com/zed-industries/zed/issues/11517 

* Removes forced prettier parser name for languages, making `auto`
command to run prettier on every file by default.
* Moves prettier configs away from plugin language declarations into
language settings

Release Notes:

- N/A

crates/language/src/language_registry.rs

@@ -715,15 +715,6 @@ impl LanguageRegistry {
             .unwrap_or_default()
     }
 
-    pub fn all_prettier_plugins(&self) -> Vec<Arc<str>> {
-        let state = self.state.read();
-        state
-            .languages
-            .iter()
-            .flat_map(|language| language.config.prettier_plugins.iter().cloned())
-            .collect()
-    }
-
     pub fn update_lsp_status(
         &self,
         server_name: LanguageServerName,