Tested versions

• Reproducible in 4.5-beta3
• Looks like it was broken by Change Node set_name to use StringName, slightly improves performance #76560

System information

Windows 11

Issue description

Renaming a node does not release the old unique name, which causes errors if you later try to use that unique name again.

Steps to reproduce

• In the editor, create a node named "foo" and mark it as having a unique name
• In the scene tree panel, rename it to "bar"
• Attempt to rename it back to "foo". This fails, reporting that the unique name "foo" is already in use

Minimal reproduction project (MRP)

unique_name_bug.zip