[BE]: Apply PERF401 autofixes from ruff (#140980)

* Automatically applies ruff rule 401. Turns loops into equivalent list comprehensions which are faster and do not leak the scope of the loop variables.
* list comprehensions not only often have better typing, but are 50+% faster than for loops on overhead. They also preserve length information etc and are better for the interpreter to optimize.
* Manually went back and made mypy happy after the change.
* Also fixed style lints in files covered by flake8 but not by pyfmt

Pull Request resolved: https://github.com/pytorch/pytorch/pull/140980
Approved by: https://github.com/justinchuby, https://github.com/malfet

torch/testing/_internal/common_utils.py

@@ -4669,8 +4669,7 @@ def _generate_indices_prefer_all_rows(rows: int, cols: int, num_indices: int) ->
 
     for r in range(rows):
         # Note that this can yield overlapping indices
-        for c in random.choices(col_indices, k=n_per_row):
-            indices.append((r, c))
+        indices.extend((r, c) for c in random.choices(col_indices, k=n_per_row))
 
     return torch.tensor(indices[:num_indices])
 
@@ -5165,9 +5164,7 @@ def get_cycles_per_ms() -> float:
     # and seems to return stable values. Therefore, we enable caching
     # using lru_cache decorator above.
     num = 10
-    vals = []
-    for _ in range(num):
-        vals.append(measure())
+    vals = [measure() for _ in range(num)]
     vals = sorted(vals)
     return mean(vals[2 : num - 2])