Merge bitcoin/bitcoin#23065: Allow UTXO locks to be written to wallet DB

d96b000e94 Make GUI UTXO lock/unlock persistent (Samuel Dobson)
077154fe69 Add release note for lockunspent change (Samuel Dobson)
719ae927dc Update lockunspent tests for lock persistence (Samuel Dobson)
f13fc16295 Allow lockunspent to store the lock in the wallet DB (Samuel Dobson)
c52789365e Allow locked UTXOs to be store in the wallet database (Samuel Dobson)

Pull request description:

  Addresses and closes #22368

  As per that issue (and its predecessor #14907), there seems to be some interest in allowing unspent outputs to be locked persistently. This PR does so by adding a flag to lockunspent to store the change in the wallet database. Defaults to false, so there is no change in default behaviour.

  Edit: GUI commit changes default behaviour. UTXOs locked/unlocked via the GUI are now persistent.

ACKs for top commit:
  achow101:
    ACK d96b000e94
  kristapsk:
    ACK d96b000e94
  lsilva01:
    Tested ACK d96b000e94 on Ubuntu 20.04
  prayank23:
    ACK d96b000e94

Tree-SHA512: 957a5bbfe7f763036796906ccb1598feb6c14c5975838be1ba24a198840bf59e83233165cb112cebae909b6b25bf27275a4d7fa425923ef6c788ff671d7a89a8

doc/release-notes-23065.md

@@ -0,0 +1,15 @@
+Notable changes
+===============
+
+Updated RPCs
+------------
+
+- `lockunspent` now optionally takes a third parameter, `persistent`, which
+causes the lock to be written persistently to the wallet database. This
+allows UTXOs to remain locked even after node restarts or crashes.
+
+GUI changes
+-----------
+
+- UTXOs which are locked via the GUI are now stored persistently in the
+wallet database, so are not lost on node shutdown or crash.