Reduce use of Widget.destroy()

On non-toplevel windows, use Container.remove() instead of Widget.destroy()
Needed for migration to GTK4
https://developer.gnome.org/gtk4/unstable/gtk-migrating-3-to-4.html#id-1.7.4.3.17

main/src/ui/add_conversation/conference_list.vala

@@ -49,7 +49,7 @@ protected class ConferenceList : FilterableList {
 
     private void remove_conference(Account account, Jid jid) {
         if (widgets.has_key(account) && widgets[account].has_key(jid)) {
-            widgets[account][jid].destroy();
+            remove(widgets[account][jid]);
             widgets[account].unset(jid);
         }
     }

main/src/ui/add_conversation/select_jid_fragment.vala

@@ -48,7 +48,7 @@ public class SelectJidFragment : Gtk.Box {
     public void set_filter(string str) {
         if (entry.text != str) entry.text = str;
 
-        foreach (AddListRow row in added_rows) row.destroy();
+        foreach (AddListRow row in added_rows) filterable_list.remove(row);
         added_rows.clear();
 
         string[] ? values = str == "" ? null : str.split(" ");

main/src/ui/conversation_content_view/conversation_item_skeleton.vala

@@ -164,7 +164,7 @@ public class ItemMetaDataHeader : Box {
             this.reorder_child(unencrypted_image, 3);
             Util.force_error_color(unencrypted_image);
         } else if (conversation.encryption == Encryption.NONE && unencrypted_image != null) {
-            unencrypted_image.destroy();
+            this.remove(unencrypted_image);
             unencrypted_image = null;
         }
     }

main/src/ui/conversation_content_view/conversation_view.vala

@@ -318,9 +318,8 @@ public class ConversationView : Box, Plugins.ConversationItemCollection, Plugins
     private void remove_item(Plugins.MetaConversationItem item) {
         ConversationItemSkeleton? skeleton = item_item_skeletons[item];
         if (skeleton != null) {
-            widgets[item].destroy();
+            main.remove(skeleton);
             widgets.unset(item);
-            skeleton.destroy();
             item_skeletons.remove(skeleton);
             item_item_skeletons.unset(item);
 
@@ -356,7 +355,7 @@ public class ConversationView : Box, Plugins.ConversationItemCollection, Plugins
 
     public void remove_notification(Widget widget) {
         notification_revealer.reveal_child = false;
-        widget.destroy();
+        notifications.remove(widget);
     }
 
     private Widget insert_new(Plugins.MetaConversationItem item) {
@@ -484,11 +483,11 @@ public class ConversationView : Box, Plugins.ConversationItemCollection, Plugins
         item_skeletons.clear();
         item_item_skeletons.clear();
         widgets.clear();
-        main.@foreach((widget) => { widget.destroy(); });
+        main.@foreach((widget) => { main.remove(widget); });
     }
 
     private void clear_notifications() {
-        notifications.@foreach((widget) => { widget.destroy(); });
+        notifications.@foreach((widget) => { notifications.remove(widget); });
         notification_revealer.transition_duration = 0;
         notification_revealer.set_reveal_child(false);
     }

main/src/ui/conversation_titlebar/occupants_entry.vala

@@ -47,7 +47,6 @@ class OccupantsWidget : MenuButton, Plugins.ConversationTitlebarWidget {
         if (conversation.type_ == Conversation.Type.GROUPCHAT) {
             OccupantMenu.View new_menu = new OccupantMenu.View(stream_interactor, conversation);
             set_popover(new_menu);
-            if (menu != null) menu.destroy();
             menu = new_menu;
         }
     }

main/src/ui/conversation_view.vala

@@ -29,7 +29,7 @@ public class ConversationView : Gtk.Overlay {
         white_revealer.visible = true;
         white_revealer.reveal_child = true;
         widget.destroy.connect(() => {
-            revealer.destroy();
+            revealer.destroy(); // GTK4: this.remove_overlay(revealer);
             white_revealer.reveal_child = false;
             chat_input.do_focus();
         });

main/src/ui/global_search.vala

@@ -118,7 +118,7 @@ public class GlobalSearch : Overlay {
     }
 
     private void clear_search() {
-        results_box.@foreach((widget) => { widget.destroy(); });
+        results_box.@foreach((widget) => { results_box.remove(widget); });
         loaded_results = 0;
     }
 

main/src/ui/manage_accounts/add_account_dialog.vala

@@ -329,7 +329,7 @@ public class AddAccountDialog : Gtk.Dialog {
     }
 
     private void set_register_form(Jid server, Xep.InBandRegistration.Form form) {
-        form_box.foreach((widget) => { widget.destroy(); });
+        form_box.foreach((widget) => { form_box.remove(widget); });
         register_title.label = _("Register on %s").printf(server.to_string());
 
         if (form.oob != null) {

main/src/ui/manage_accounts/dialog.vala

@@ -128,7 +128,7 @@ public class Dialog : Gtk.Dialog {
         ok_button.label = _("Remove");
         ok_button.get_style_context().add_class("destructive-action");
         if (msg.run() == Gtk.ResponseType.OK) {
-            account_item.destroy();
+            account_list.remove(account_item);
             if (account_item.account.enabled) account_disabled(account_item.account);
             account_item.account.remove();
             if (account_list.get_row_at_index(0) != null) {

main/src/ui/occupant_menu/view.vala

@@ -119,7 +119,7 @@ public class View : Popover {
             
         }
 
-        if (jid_menu != null) jid_menu.destroy();
+        if (jid_menu != null) stack.remove(jid_menu);
         stack.add_named(outer_box, "menu");
         stack.visible_child_name = "menu";
         jid_menu = outer_box;