[PR #10136/937d92ee backport][stable-10] pickle cache plugin, avoid extra steps in DT (#10144)

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



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(cherry picked from commit 937d92ee25)

Co-authored-by: Brian Coca <bcoca@users.noreply.github.com>
Co-authored-by: Felix Fontein <felix@fontein.de>

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