Remove fake base class ipaddress._BaseInterface (#12949)

Also make hostmask a property to improve stubtest

stdlib/@tests/stubtest_allowlists/common.txt

@@ -59,8 +59,6 @@ importlib.abc.Loader.exec_module  # See Lib/importlib/_abc.py. Might be defined
 importlib.abc.MetaPathFinder.find_spec  # Not defined on the actual class, but expected to exist.
 importlib.abc.PathEntryFinder.find_spec  # Not defined on the actual class, but expected to exist.
 importlib.machinery.ExtensionFileLoader.get_filename  # Wrapped with _check_name decorator which changes runtime signature
-ipaddress.IPv4Interface.hostmask
-ipaddress.IPv6Interface.hostmask
 ipaddress._BaseAddress.is_global
 ipaddress._BaseAddress.is_link_local
 ipaddress._BaseAddress.is_loopback

stdlib/ipaddress.pyi

@@ -128,19 +128,6 @@ class _BaseNetwork(_IPAddressBase, Generic[_A]):
     @property
     def hostmask(self) -> _A: ...
 
-class _BaseInterface(_BaseAddress, Generic[_A, _N]):
-    hostmask: _A
-    netmask: _A
-    network: _N
-    @property
-    def ip(self) -> _A: ...
-    @property
-    def with_hostmask(self) -> str: ...
-    @property
-    def with_netmask(self) -> str: ...
-    @property
-    def with_prefixlen(self) -> str: ...
-
 class _BaseV4:
     @property
     def version(self) -> Literal[4]: ...
@@ -154,9 +141,21 @@ class IPv4Address(_BaseV4, _BaseAddress):
 
 class IPv4Network(_BaseV4, _BaseNetwork[IPv4Address]): ...
 
-class IPv4Interface(IPv4Address, _BaseInterface[IPv4Address, IPv4Network]):
+class IPv4Interface(IPv4Address):
+    netmask: IPv4Address
+    network: IPv4Network
     def __eq__(self, other: object) -> bool: ...
     def __hash__(self) -> int: ...
+    @property
+    def hostmask(self) -> IPv4Address: ...
+    @property
+    def ip(self) -> IPv4Address: ...
+    @property
+    def with_hostmask(self) -> str: ...
+    @property
+    def with_netmask(self) -> str: ...
+    @property
+    def with_prefixlen(self) -> str: ...
 
 class _BaseV6:
     @property
@@ -184,9 +183,21 @@ class IPv6Network(_BaseV6, _BaseNetwork[IPv6Address]):
     @property
     def is_site_local(self) -> bool: ...
 
-class IPv6Interface(IPv6Address, _BaseInterface[IPv6Address, IPv6Network]):
+class IPv6Interface(IPv6Address):
+    netmask: IPv6Address
+    network: IPv6Network
     def __eq__(self, other: object) -> bool: ...
     def __hash__(self) -> int: ...
+    @property
+    def hostmask(self) -> IPv6Address: ...
+    @property
+    def ip(self) -> IPv6Address: ...
+    @property
+    def with_hostmask(self) -> str: ...
+    @property
+    def with_netmask(self) -> str: ...
+    @property
+    def with_prefixlen(self) -> str: ...
 
 def v4_int_to_packed(address: int) -> bytes: ...
 def v6_int_to_packed(address: int) -> bytes: ...