Merge bitcoin-core/gui#493: qt: Handle Android back key in the Node window

a56a1049380b0acb532681484fbb675c3b2ff365 qt: Handle Android back key in the Node window (Hennadii Stepanov)
f045f987171c3960c12813538b9f19a54a50b4f8 qt, android: Add GUIUtil::IsEscapeOrBack helper (Hennadii Stepanov)

Pull request description:

  On master (4633199cc8a466b8a2cfa14ba9d7793dd4c469f4) there are no means to return from the Node window to the main one on Android.

  This PR assigns this functionality to the Android back key:

  ![Screenshot_1638395318](https://user-images.githubusercontent.com/32963518/144320316-af5599ac-0379-40e6-9887-7f5ee30b97ae.png)

ACKs for top commit:
  icota:
    utACK a56a104938

Tree-SHA512: 379c1ad8c6bffa037e861b88c66eb33872d7f7d54aa2f76289a51c55d79a37a0c16262b20f22d00fda11522c7df1f3561c1ceae34cd7a85da94aee4c6cdcfaaf

src/qt/guiutil.h

@@ -428,6 +428,15 @@ namespace GUIUtil
      */
     void ShowModalDialogAndDeleteOnClose(QDialog* dialog);
 
+    inline bool IsEscapeOrBack(int key)
+    {
+        if (key == Qt::Key_Escape) return true;
+#ifdef Q_OS_ANDROID
+        if (key == Qt::Key_Back) return true;
+#endif // Q_OS_ANDROID
+        return false;
+    }
+
 } // namespace GUIUtil
 
 #endif // BITCOIN_QT_GUIUTIL_H

src/qt/rpcconsole.cpp

@@ -14,6 +14,7 @@
 #include <netbase.h>
 #include <qt/bantablemodel.h>
 #include <qt/clientmodel.h>
+#include <qt/guiutil.h>
 #include <qt/peertablesortproxy.h>
 #include <qt/platformstyle.h>
 #include <qt/walletmodel.h>
@@ -910,8 +911,7 @@ void RPCConsole::clear(bool keep_prompt)
 
 void RPCConsole::keyPressEvent(QKeyEvent *event)
 {
-    if(windowType() != Qt::Widget && event->key() == Qt::Key_Escape)
-    {
+    if (windowType() != Qt::Widget && GUIUtil::IsEscapeOrBack(event->key())) {
         close();
     }
 }