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

stubs/Markdown/markdown/core.pyi

@@ -1,3 +1,4 @@
+from _typeshed import Self
 from typing import Any, BinaryIO, Callable, ClassVar, Mapping, Sequence, Text, TextIO
 from typing_extensions import Literal
 from xml.etree.ElementTree import Element
@@ -30,7 +31,7 @@ class Markdown:
     def registerExtensions(self, extensions: Sequence[Extension | str], configs: Mapping[str, Mapping[str, Any]]) -> Markdown: ...
     def build_extension(self, ext_name: Text, configs: Mapping[str, str]) -> Extension: ...
     def registerExtension(self, extension: Extension) -> Markdown: ...
-    def reset(self: Markdown) -> Markdown: ...
+    def reset(self: Self) -> Self: ...
     def set_output_format(self, format: Literal["xhtml", "html"]) -> Markdown: ...
     def is_block_level(self, tag: str) -> bool: ...
     def convert(self, source: Text) -> Text: ...