qt: Add WalletFrame::currentWalletSet signal

The connection of the WalletFrame::currentWalletSet signal to
the BitcoinGUI::updateWalletStatus is a shorter and more descriptive way
to call both the setHDStatus and setEncryptionStatus member functions of
the BitcoinGUI class in comparison to using of the
WalletView::updateEncryptionStatus slot.

src/qt/walletframe.cpp

@@ -109,7 +109,8 @@ void WalletFrame::setCurrentWallet(WalletModel* wallet_model)
     walletView->updateGeometry();
 
     walletStack->setCurrentWidget(walletView);
-    walletView->updateEncryptionStatus();
+
+    Q_EMIT currentWalletSet();
 }
 
 void WalletFrame::removeWallet(WalletModel* wallet_model)