pickle cache plugin, avoid extra steps in DT (#10136)

* pickle cache plugin, avoid extra steps in DT

* clog

* Update changelogs/fragments/10136-cache-pickle-json.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

---------

Co-authored-by: Felix Fontein <felix@fontein.de>

changelogs/fragments/10136-cache-pickle-json.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - pickle cache plugin - avoid extra JSON serialization with ansible-core >= 2.19 (https://github.com/ansible-collections/community.general/pull/10136).

plugins/cache/pickle.py

@@ -56,6 +56,7 @@ class CacheModule(BaseFileCacheModule):
     """
     A caching module backed by pickle files.
     """
+    _persistent = False  # prevent unnecessary JSON serialization and key munging
 
     def _load(self, filepath):
         # Pickle is a binary format