[docker] Run stubtest on Windows to cover the named pipe transport (#16422)

docker-py installs pywin32 on Windows, so docker.transport.npipeconn
and docker.transport.npipesocket import there and stubtest reported the
global allowlist entries for them as unused. Move those entries to the
linux and darwin allowlists, where the modules fail to import, and add
win32 to ci-platforms so the npipe stubs are checked against the
runtime.

Author: SharoonSharif

stubs/docker/@tests/stubtest_allowlist.txt

@@ -1,6 +1,4 @@
-# additional requirements are needed, e.g. win32 apis
-docker.transport.npipeconn
-docker.transport.npipesocket
+# requires paramiko, which is only installed with the ssh extra
 docker.transport.sshconn
 
 # model is always set by child classes

stubs/docker/@tests/stubtest_allowlist_darwin.txt

@@ -0,0 +1,3 @@
+# the named pipe transport requires pywin32, which is only installed on Windows
+docker.transport.npipeconn
+docker.transport.npipesocket

stubs/docker/@tests/stubtest_allowlist_linux.txt

@@ -0,0 +1,3 @@
+# the named pipe transport requires pywin32, which is only installed on Windows
+docker.transport.npipeconn
+docker.transport.npipesocket

stubs/docker/METADATA.toml

@@ -2,3 +2,6 @@ version = "7.2.*"
 upstream-repository = "https://github.com/docker/docker-py"
 dependencies = ["types-requests", "urllib3>=2"]
 optional-dependencies = ["types-paramiko"]
+
+[tool.stubtest]
+ci-platforms = ["linux", "win32"]