Merge #9662: Add createwallet "disableprivatekeys" option: a sane mode for watchonly-wallets

a3fa4d6a6a QA: Fix bug in -usecli logic that converts booleans to non-lowercase strings (Jonas Schnelli)
4704e5f074 [QA] add createwallet disableprivatekey test (Jonas Schnelli)
c7b8f343e9 [Qt] Disable creating receive addresses when private keys are disabled (Jonas Schnelli)
2f15c2bc20 Add disable privatekeys option to createwallet (Jonas Schnelli)
cebefba085 Add option to disable private keys during internal wallet creation (Jonas Schnelli)
9995a602a6 Add facility to store wallet flags (64 bits) (Jonas Schnelli)

Pull request description:

  This mode ('createwallet {"disableprivatekeys": true}') is intended for a sane pure watch-only mode, ideal for a use-case where one likes to use Bitcoin-Core in conjunction with a hardware-wallet or another solutions for cold-storage.

  Since we have support for custom change addresses in `fundrawtransaction`, pure watch-only wallets including coin-selection are possible and do make sense for some use cases.

  This new mode disables all forms of private key generation and ensure that no mix between hot and cold keys are possible.

Tree-SHA512: 3ebe7e8d54c4d4e5f790c348d4c292d456f573960a5b04d69ca5ef43a9217c7e7671761c6968cdc56f9a8bc235f3badd358576651af9f10855a0eb731f3fc508

test/functional/test_runner.py

@@ -98,6 +98,8 @@ BASE_SCRIPTS = [
     'mempool_persist.py',
     'wallet_multiwallet.py',
     'wallet_multiwallet.py --usecli',
+    'wallet_disableprivatekeys.py',
+    'wallet_disableprivatekeys.py --usecli',
     'interface_http.py',
     'rpc_psbt.py',
     'rpc_users.py',