Fix load error popup showing on every progress dialog

[Hilderin]

• Fixes partially editor_doc_cache errors on editor startup #96798

That's a funny regression from #93064.

When starting up the editor, if a file is read-only, a "Load errors" dialog should open to display the I/O errors. However, with the addition of a progress bar during editor startup, the "Load errors" dialog was opened while the Progress dialog was active, making the Progress dialog the parent of the "Load errors" dialog.

This caused the issue where the "Load errors" dialog would flash every time the Progress dialog was shown, displaying the same error from the editor startup repeatedly.

The reason why the error for the editor_doc_cache file only occurred in the dev build is that the case is not reconstructed every time in the release build.

Also, I could not figure out why adb.exe was locking the file. I suspect there's an issue with Android Studio, but I'm not sure.

I was tempted to add a removal of the .tmp file if the save was not successful, but I guess that would defeat the purpose of the backup_save_enabled feature.

I modified EditorNode to prevent displayed the "Load errors" while a Progress dialog is opened and when the progress is closed, I open the "Load errors" dialog.

[KoBeWi]

It's difficult to test it, because the bug happens randomly, but the individual dialogs still work correctly.

Note that #96798 was about errors at startup, the progress bug was only a byproduct. I don't think this fix fully resolves the issue.

[akien-mga]

Thanks!