Auto merge of #3517 - mdr0id:3388_persist_wallet, r=str4d

Sapling support for persisting wallet to disk

Closes #3388. Closes #3061.

qa/pull-tester/rpc-tests.sh

@@ -24,7 +24,8 @@ testScripts=(
     'wallet_mergetoaddress.py'
     'wallet.py'
     'wallet_overwintertx.py'
-#    'wallet_nullifiers.py'
+    'wallet_persistence.py'
+    'wallet_nullifiers.py'
     'wallet_1941.py'
     'wallet_addresses.py'
     'wallet_sapling.py'
@@ -45,7 +46,7 @@ testScripts=(
     'zapwallettxes.py'
     'proxy_test.py'
     'merkle_blocks.py'
-#    'fundrawtransaction.py'
+    'fundrawtransaction.py'
     'signrawtransactions.py'
     'signrawtransaction_offline.py'
     'walletbackup.py'