dvc.fs: rename fs.utils to fs.generic

In the spirit of fsspec.generic, it is for cross-filesystem operations.
Trying to avoid `fs.utils` as much as possible, but we have some
functions that are really utilities coming, so I am making a place
for them. :)

tests/func/test_import.py

@@ -307,9 +307,9 @@ def test_download_error_pulling_imported_stage(tmp_dir, dvc, erepo_dir):
     remove("foo_imported")
     remove(dst_cache)
 
-    with patch("dvc.fs.utils.transfer", side_effect=Exception), pytest.raises(
-        DownloadError
-    ):
+    with patch(
+        "dvc.fs.generic.transfer", side_effect=Exception
+    ), pytest.raises(DownloadError):
         dvc.pull(["foo_imported.dvc"])