internal: Make static analysis more happy (#8767)

* make functions used in 1 file static

* fix invalid substr param -1

* give default initializer to borderGradier

* move RASSERT from printf to std::print

src/desktop/Window.cpp

@@ -473,7 +473,7 @@ PHLWINDOW CWindow::x11TransientFor() {
     return nullptr;
 }
 
-void unregisterVar(void* ptr) {
+static void unregisterVar(void* ptr) {
     ((CBaseAnimatedVariable*)ptr)->unregister();
 }