Make more tests run on Windows (#8446)

* Remove worker Wait() call due to SIGCHLD being ignored

* Port _pid_alive to Windows

* Show PID as well as TID in glog

* Update TensorFlow version for Python 3.8 on Windows

* Handle missing Pillow on Windows

* Work around dm-tree PermissionError on Windows

* Fix some lint errors on Windows with Python 3.8

* Simplify torch requirements

* Quiet git clean

* Handle finalizer issues

* Exit with the signal number

* Get rid of wget

* Fix some Windows compatibility issues with tests

Co-authored-by: Mehrdad <noreply@github.com>

python/ray/tests/test_advanced.py

@@ -334,19 +334,19 @@ def test_identical_function_names(ray_start_regular):
         return 1
 
     @ray.remote  # noqa: F811
-    def g():
+    def g():  # noqa: F811
         return 2
 
     @ray.remote  # noqa: F811
-    def g():
+    def g():  # noqa: F811
         return 3
 
     @ray.remote  # noqa: F811
-    def g():
+    def g():  # noqa: F811
         return 4
 
     @ray.remote  # noqa: F811
-    def g():
+    def g():  # noqa: F811
         return 5
 
     result_values = ray.get([g.remote() for _ in range(num_calls)])