Moving folder AA to folder BB which have folder with same name(AA) cause error moving instead merge.

[qarmin]

Godot version:
3.1 b17e71b

Windows 10

Issue description:
When I try to copy folder with name AA to folder BB which contain folder with name AA, error "Error moving:" was occur.

I think that Godot should merge this folder to one.

When we paste files, the warning message should stay as is "Please Confirm... ... Overwrite Cancel "

But when we paste folders, I think the warning should change text "Overwrite" to "Merge and Overwrite".

Steps to reproduce:

1. Create res://AA folder
2. Create res://BB folder
3. Create res://BB/AA folder
4. Try to cut folder res://AA and paste it to res://BB

https://streamable.com/vibga

[akien-mga]

To anyone interested in implementing this, please take the feedback in #22855 into account.

Especially, there should be a confirmation dialog before any kind of merge or overwrite operation.