Editor: forbid deleting inherited metadata properties

[dustdfg]

Fixes https://github.com/godotengine/godot/issues/97596

Before:

https://github.com/user-attachments/assets/7a916b20-ffca-4ca1-ad7b-de0a372a7080

After:

https://github.com/user-attachments/assets/fd2ea1ec-0dcd-4b19-8ad6-3e69c1e14928

[KoBeWi]

Crash when editing Resource:

CrashHandlerException: Program crashed
Engine version: Godot Engine v4.4.dev.custom_build (0b7c6e6b50d230786a1258d8f69bce5eb30b9568)
Dumping the backtrace. Please include this when reporting the bug to the project developer.
[0] PropertyUtils::get_property_default_value (C:\godot_source\scene\property_utils.cpp:142)
[1] EditorInspector::update_tree (C:\godot_source\editor\editor_inspector.cpp:3461)
[2] EditorInspector::_notification (C:\godot_source\editor\editor_inspector.cpp:4153)
[3] EditorInspector::_notificationv (C:\godot_source\editor\editor_inspector.h:481)
[4] Object::notification (C:\godot_source\core\object\object.cpp:878)
[5] SceneTree::_process_group (C:\godot_source\scene\main\scene_tree.cpp:1031)
[6] SceneTree::_process (C:\godot_source\scene\main\scene_tree.cpp:1108)
[7] SceneTree::process (C:\godot_source\scene\main\scene_tree.cpp:590)
[8] Main::iteration (C:\godot_source\main\main.cpp:4398)
[9] OS_Windows::run (C:\godot_source\platform\windows\os_windows.cpp:1772)
[10] widechar_main (C:\godot_source\platform\windows\godot_windows.cpp:181)
[11] _main (C:\godot_source\platform\windows\godot_windows.cpp:206)
[12] main (C:\godot_source\platform\windows\godot_windows.cpp:220)
[13] WinMain (C:\godot_source\platform\windows\godot_windows.cpp:234)
[14] __scrt_common_main_seh (D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288)
[15] <couldn't map PC to fn name>
-- END OF BACKTRACE --

You are casting to Node, but don't check whether the cast succeeded (it will be null for non-Nodes)

[dustdfg]

I am not going to do anything to update this PR. But it is not bad in IMO so I am not closing it... Over time some merge conflicts can occur... There are people with "write access" so if you need it you can correct it. I am abandoning this PR... If you want close it

[KoBeWi]

This is already in mergeable state.

[Repiteo]

Thanks!