chore: rename some helpers on the Fs trait (#20097)

Rename some of the helper methods on the Fs trait to be suffixed with
`_sync` / `_async`, in preparation of the introduction of more async
methods for some helpers.

Also adds a `read_text_file_async` helper to complement the renamed
`read_text_file_sync` helper.

ext/fs/interface.rs

@@ -233,25 +233,31 @@ pub trait FileSystem: std::fmt::Debug + MaybeSend + MaybeSync {
     Ok(buf)
   }
 
-  fn is_file(&self, path: &Path) -> bool {
+  fn is_file_sync(&self, path: &Path) -> bool {
     self.stat_sync(path).map(|m| m.is_file).unwrap_or(false)
   }
 
-  fn is_dir(&self, path: &Path) -> bool {
+  fn is_dir_sync(&self, path: &Path) -> bool {
     self
       .stat_sync(path)
       .map(|m| m.is_directory)
       .unwrap_or(false)
   }
 
-  fn exists(&self, path: &Path) -> bool {
+  fn exists_sync(&self, path: &Path) -> bool {
     self.stat_sync(path).is_ok()
   }
 
-  fn read_to_string(&self, path: &Path) -> FsResult<String> {
+  fn read_text_file_sync(&self, path: &Path) -> FsResult<String> {
     let buf = self.read_file_sync(path)?;
     String::from_utf8(buf).map_err(|err| {
       std::io::Error::new(std::io::ErrorKind::InvalidData, err).into()
     })
   }
+  async fn read_text_file_async(&self, path: PathBuf) -> FsResult<String> {
+    let buf = self.read_file_async(path).await?;
+    String::from_utf8(buf).map_err(|err| {
+      std::io::Error::new(std::io::ErrorKind::InvalidData, err).into()
+    })
+  }
 }