Change InputMethod::show() and InputMethod::hide() to not change active state.

Qt usually request InputMethod::hide() upon unfocus, but
InputMethod::show() is actually never called if focus transfer is done
by keyboard, which leads to a permanent disabled input method state.

It can be easily reproduced with a window with two text field, e.g.
QFileDialog, by pressing tab to switch the focused widget.

The semantics of hide/show should not deactivate the input method.
Instead, it should simply hide/show the input panel. Also it should not
be a hard request for input method to permanently hide the window. When
input method asked to show it again, the input panel window should be
shown.

src/inputmethod.cpp

@@ -111,12 +111,24 @@ void InputMethod::init()
 
 void InputMethod::show()
 {
+    if (m_inputClient) {
+        m_inputClient->showClient();
+        updateInputPanelState();
+    }
     setActive(true);
 }
 
 void InputMethod::hide()
 {
-    setActive(false);
+    if (m_inputClient) {
+        m_inputClient->hideClient();
+        updateInputPanelState();
+    }
+    auto inputContext = waylandServer()->inputMethod()->context();
+    if (!inputContext) {
+        return;
+    }
+    inputContext->sendReset();
 }
 
 bool InputMethod::touchEventTriggered() const

src/inputpanelv1client.cpp

@@ -49,6 +49,7 @@ void InputPanelV1Client::showOverlayPanel()
     setOutput(nullptr);
     m_mode = Overlay;
     reposition();
+    showClient();
     setReadyForPainting();
 }
 
@@ -57,6 +58,7 @@ void InputPanelV1Client::showTopLevel(OutputInterface *output, InputPanelSurface
     Q_UNUSED(position);
     m_mode = Toplevel;
     setOutput(output);
+    showClient();
 }
 
 void InputPanelV1Client::allow()