PY-26456 Send change event on setting up new SDK

This event is required to revalidate the new project dialog form.

Also updated the border rendering in the SDK list.

python/python-community-configure/src/com/jetbrains/python/newProject/steps/PythonSdkChooserCombo.java

@@ -117,6 +117,7 @@ public class PythonSdkChooserCombo extends ComboboxWithBrowseButton {
         selectedSdk = oldSelectedSdk;
       }
       comboBox.setModel(new CollectionComboBoxModel<>(allSdks, selectedSdk));
+      notifyChanged(null);
     });
   }
 

python/src/com/jetbrains/python/sdk/PySdkListCellRenderer.kt

@@ -23,8 +23,9 @@ import com.intellij.openapi.util.IconLoader
 import com.intellij.openapi.util.io.FileUtil
 import com.intellij.ui.ColoredListCellRenderer
 import com.intellij.ui.LayeredIcon
-import com.intellij.ui.ListCellRendererWrapper
 import com.intellij.ui.SimpleTextAttributes
+import com.intellij.ui.TitledSeparator
+import com.intellij.util.ui.JBUI
 import com.jetbrains.python.sdk.flavors.PythonSdkFlavor
 import java.awt.Component
 import javax.swing.Icon
@@ -37,7 +38,9 @@ open class PySdkListCellRenderer(private val sdkModifiers: Map<Sdk, SdkModificat
   override fun getListCellRendererComponent(list: JList<out Any>?, value: Any?, index: Int, selected: Boolean,
                                             hasFocus: Boolean): Component =
     when (value) {
-      SEPARATOR -> ListCellRendererWrapper.createSeparator(null)
+      SEPARATOR -> TitledSeparator(null).apply {
+        border = JBUI.Borders.empty()
+      }
       else -> super.getListCellRendererComponent(list, value, index, selected, hasFocus)
     }