core: Use less confusing name for Platform::supportsQpaContext()

Platform::supportsQpaContext() indicates if the EGL display supports
surfaceless contexts, so reflect that in the method name.

(cherry picked from commit 29fbe27f)

platform.cpp

@@ -413,7 +413,7 @@ void Platform::warpPointer(const QPointF &globalPos)
     Q_UNUSED(globalPos)
 }
 
-bool Platform::supportsQpaContext() const
+bool Platform::supportsSurfacelessContext() const
 {
     if (Compositor *c = Compositor::self()) {
         return c->scene()->supportsSurfacelessContext();

platform.h

@@ -100,7 +100,7 @@ public:
      * Whether our Compositing EGL display allows a surface less context
      * so that a sharing context could be created.
      */
-    virtual bool supportsQpaContext() const;
+    bool supportsSurfacelessContext() const;
     /**
      * The EGLDisplay used by the compositing scene.
      */

plugins/qpa/window.cpp

@@ -146,7 +146,7 @@ void Window::unmap()
 
 EGLSurface Window::eglSurface() const
 {
-    if (kwinApp()->platform()->supportsQpaContext()) {
+    if (kwinApp()->platform()->supportsSurfacelessContext()) {
         return EGL_NO_SURFACE;
     }
     return kwinApp()->platform()->sceneEglSurface();