Always use _typeshed.Self, where applicable (#6880)

* Always use `_typeshed.Self`, where applicable

* Revert changes to `google-cloud-ndb` (ambiguous)

* Remove empty line added by script

* Revert changes to `stubs/python-dateutil/dateutil/relativedelta.pyi`

* Manually add a few more that the script missed

* Improve `filelock` annotation

Source code here: https://github.com/tox-dev/py-filelock/blob/79ec7b2826e33b982fe83b057f359448b9d966ba/src/filelock/_api.py#L207

* Improve `opentracing/scope` annotation

Source code here: https://github.com/opentracing/opentracing-python/blob/3e1d357a348269ef54d67f761302fab93dbfc0f7/opentracing/scope.py#L71

* Improve `redis/client` stub

Source code here: https://github.com/redis/redis-py/blob/15f315a496c3267c8cbcc6d6d9c6005ea4d4a4d5/redis/client.py#L1217

* Improve `redis/lock` annotation

Source code here: https://github.com/redis/redis-py/blob/15f315a496c3267c8cbcc6d6d9c6005ea4d4a4d5/redis/lock.py#L155

* Improve `requests/models` annotation

Source code here: https://github.com/psf/requests/blob/d718e753834b84018014a23d663369ac27d1ab9c/requests/models.py#L653

stdlib/email/_header_value_parser.pyi

@@ -1,11 +1,10 @@
 import sys
+from _typeshed import Self
 from email.errors import HeaderParseError, MessageDefect
 from email.policy import Policy
-from typing import Any, Iterable, Iterator, Pattern, TypeVar, Union
+from typing import Any, Iterable, Iterator, Pattern, Union
 from typing_extensions import Final
 
-_T = TypeVar("_T")
-
 WSP: Final[set[str]]
 CFWS_LEADER: Final[set[str]]
 SPECIALS: Final[set[str]]
@@ -327,7 +326,7 @@ class Terminal(str):
     syntactic_break: bool
     token_type: str
     defects: list[MessageDefect]
-    def __new__(cls: type[_T], value: str, token_type: str) -> _T: ...
+    def __new__(cls: type[Self], value: str, token_type: str) -> Self: ...
     def pprint(self) -> None: ...
     @property
     def all_defects(self) -> list[MessageDefect]: ...