Add type to some asyncio.transports methods (#8756)

`WriteTransport.write`, `WriteTransport.writelines` and `DatagramTransport.sendto` methods only accept `bytes` trying an other type raises an exception

`BaseTransport._extra` is a dictionary with string as key

stdlib/asyncio/transports.pyi

@@ -1,14 +1,14 @@
 from asyncio.events import AbstractEventLoop
 from asyncio.protocols import BaseProtocol
-from collections.abc import Mapping
+from collections.abc import Iterable, Mapping
 from socket import _Address
 from typing import Any
 
 __all__ = ("BaseTransport", "ReadTransport", "WriteTransport", "Transport", "DatagramTransport", "SubprocessTransport")
 
 class BaseTransport:
-    def __init__(self, extra: Mapping[Any, Any] | None = ...) -> None: ...
-    def get_extra_info(self, name: Any, default: Any = ...) -> Any: ...
+    def __init__(self, extra: Mapping[str, Any] | None = ...) -> None: ...
+    def get_extra_info(self, name: str, default: Any = ...) -> Any: ...
     def is_closing(self) -> bool: ...
     def close(self) -> None: ...
     def set_protocol(self, protocol: BaseProtocol) -> None: ...
@@ -23,8 +23,8 @@ class WriteTransport(BaseTransport):
     def set_write_buffer_limits(self, high: int | None = ..., low: int | None = ...) -> None: ...
     def get_write_buffer_size(self) -> int: ...
     def get_write_buffer_limits(self) -> tuple[int, int]: ...
-    def write(self, data: Any) -> None: ...
-    def writelines(self, list_of_data: list[Any]) -> None: ...
+    def write(self, data: bytes) -> None: ...
+    def writelines(self, list_of_data: Iterable[bytes]) -> None: ...
     def write_eof(self) -> None: ...
     def can_write_eof(self) -> bool: ...
     def abort(self) -> None: ...
@@ -32,7 +32,7 @@ class WriteTransport(BaseTransport):
 class Transport(ReadTransport, WriteTransport): ...
 
 class DatagramTransport(BaseTransport):
-    def sendto(self, data: Any, addr: _Address | None = ...) -> None: ...
+    def sendto(self, data: bytes, addr: _Address | None = ...) -> None: ...
     def abort(self) -> None: ...
 
 class SubprocessTransport(BaseTransport):
@@ -44,4 +44,4 @@ class SubprocessTransport(BaseTransport):
     def kill(self) -> None: ...
 
 class _FlowControlMixin(Transport):
-    def __init__(self, extra: Mapping[Any, Any] | None = ..., loop: AbstractEventLoop | None = ...) -> None: ...
+    def __init__(self, extra: Mapping[str, Any] | None = ..., loop: AbstractEventLoop | None = ...) -> None: ...