Fold in changes
Merge branch 'release-0.6.0'
Add changes file (#5895).
Make client db access script defer decryption.
Add encrypted field to sync db (#5895).
Store non-encrypted docs in the sync db (#5985).
Insert received docs in sync db after decryption (#5985).
Store all received docs in sync db (#5895).
On sync, fetch all docs before decrypting.
Allow deferred decryption without deferred encryption.
Avoid deadlocks when cancelling failed sync threads.
Make sync database multiprocessing-safe.
Refactor secrets out of main soledad client class.
Fix tests after many changes in client.