Merge bitcoin/bitcoin#19101: refactor: remove ::vpwallets and related global variables

62a09a3077 refactor: remove ::vpwallets and related global variables (Russell Yanofsky)

Pull request description:

  Get rid of global wallet list variables by moving them to WalletContext struct

  - [`cs_wallets`](e638acf697/src/wallet/wallet.cpp (L56)) is now [`WalletContext::wallet_mutex`](4be544c7ec/src/wallet/context.h (L37))
  - [`vpwallets`](e638acf697/src/wallet/wallet.cpp (L57)) is now [`WalletContext::wallets`](4be544c7ec/src/wallet/context.h (L38))
  - [`g_load_wallet_fns`](e638acf697/src/wallet/wallet.cpp (L58)) is now [`WalletContext::wallet_load_fns`](4be544c7ec/src/wallet/context.h (L39))

ACKs for top commit:
  achow101:
    ACK 62a09a3077
  meshcollider:
    re-utACK 62a09a3077

Tree-SHA512: 74428180d57b4214c3d96963e6ff43e8778f6f23b6880262d1272f2de67d02714fdc3ebb558f62e48655b221a642c36f80ef37c8f89d362e2d66fd93cbf03b8f

src/interfaces/wallet.h

@@ -332,6 +332,9 @@ public:
    //! loaded at startup or by RPC.
    using LoadWalletFn = std::function<void(std::unique_ptr<Wallet> wallet)>;
    virtual std::unique_ptr<Handler> handleLoadWallet(LoadWalletFn fn) = 0;
+
+   //! Return pointer to internal context, useful for testing.
+   virtual WalletContext* context() { return nullptr; }
 };
 
 //! Information about one wallet address.
@@ -410,7 +413,7 @@ struct WalletTxOut
 
 //! Return implementation of Wallet interface. This function is defined in
 //! dummywallet.cpp and throws if the wallet component is not compiled.
-std::unique_ptr<Wallet> MakeWallet(const std::shared_ptr<CWallet>& wallet);
+std::unique_ptr<Wallet> MakeWallet(WalletContext& context, const std::shared_ptr<CWallet>& wallet);
 
 //! Return implementation of ChainClient interface for a wallet client. This
 //! function will be undefined in builds where ENABLE_WALLET is false.