ruff: enable TC — flake8-type-checking (#11368)

## Problem

`TYPE_CHECKING` is used inconsistently across Python tests.

## Summary of changes
- Update `ruff`: 0.7.0 -> 0.11.2
- Enable TC (flake8-type-checking):
https://docs.astral.sh/ruff/rules/#flake8-type-checking-tc
- (auto)fix all new issues

test_runner/performance/test_random_writes.py

@@ -2,11 +2,14 @@ from __future__ import annotations
 
 import random
 from contextlib import closing
+from typing import TYPE_CHECKING
 
 from fixtures.benchmark_fixture import MetricReport
-from fixtures.compare_fixtures import PgCompare
 from fixtures.utils import query_scalar
 
+if TYPE_CHECKING:
+    from fixtures.compare_fixtures import PgCompare
+
 
 # This is a clear-box test that demonstrates the worst case scenario for the
 # "1 segment per layer" implementation of the pageserver. It writes to random