Merge #13111: Add unloadwallet RPC

fe65bdec2 bugfix: Delete walletView in WalletFrame::removeWallet (João Barbosa)
0b82bac76 bugfix: Remove dangling wallet env instance (João Barbosa)
0ee77b207 ui: Support wallets unloaded dynamically (João Barbosa)
9f9b50d5f doc: Add release notes for unloadwallet RPC (João Barbosa)
ccbf7ae74 test: Wallet methods are disabled when no wallet is loaded (João Barbosa)
4940a20a4 test: Add functional tests for unloadwallet RPC (João Barbosa)
6608c369b rpc: Add unloadwallet RPC (João Barbosa)
537efe19e rpc: Extract GetWalletNameFromJSONRPCRequest from GetWalletForJSONRPCRequest (João Barbosa)

Pull request description:

  This patch adds wallet unload feature via RPC. It also adds UI support for unloaded wallets.

Tree-SHA512: 7c7f9f32f7a2266d2df574aa6b95f993c3dc82736f93304562122beb8756fb28cd22d03866b48f493c747441f22d30e196b098dec435cc25e035633f090351ea

doc/release-notes-pr10740.md

@@ -1,9 +1,10 @@
 Dynamic loading and creation of wallets
 ---------------------------------------
 
-Previously, wallets could only be loaded or created at startup, by specifying `-wallet` parameters on the command line or in the bitcoin.conf file. It is now possible to load and create wallets dynamically at runtime:
+Previously, wallets could only be loaded or created at startup, by specifying `-wallet` parameters on the command line or in the bitcoin.conf file. It is now possible to load, create and unload wallets dynamically at runtime:
 
 - Existing wallets can be loaded by calling the `loadwallet` RPC. The wallet can be specified as file/directory basename (which must be located in the `walletdir` directory), or as an absolute path to a file/directory.
 - New wallets can be created (and loaded) by calling the `createwallet` RPC. The provided name must not match a wallet file in the `walletdir` directory or the name of a wallet that is currently loaded.
+- Loaded wallets can be unloaded by calling the `unloadwallet` RPC.
 
 This feature is currently only available through the RPC interface.