Windows async - handle trailing junk output (#85820) (#85829)

Add handling for when a PowerShell module emits more than just the
module result JSON. The behaviour reflects the Python async wrapper
where trailing data after the module result will emit a warning.

(cherry picked from commit aad9fbd4f5)

changelogs/fragments/win_async-junk-output.yml

@@ -0,0 +1,3 @@
+bugfixes:
+  - >-
+    Windows async - Handle running PowerShell modules with trailing data after the module result