Nested permanent elements replaced with clones

[pardo-bsso]

Describe the bug

When having a document structure where an element with tagged with data-turbolinks-permanent is placed inside another one also marked as permanent (depth of hierarchy does not matter) the inner ones are replaced by clones, and thus they lose all their existing event handlers and data.

To Reproduce
There's a bare bones demonstration at https://tangopardo.com.ar/pub/github/turbolinks_nested_issue_demo/index.html
Go to that site, click on 'go to test 2' and hit the 'Compare elements with old dom' button.

Expected behavior
Elements with data-turbolinks-permanent inside others that are permanent are correctly reinserted after a navigation.
In the demo case parent, child-0, child-1 and child-2 should be the same.
Interestingly, if in test2.html I remove data-turbolinks-permanent from child-2 it is correctly re-attached.

Details (please complete the following information):

• Operating System: Linux x86-64
• Browser: Firefox 80, Chrome 83.0.4103.61
• Turbolinks Version: v5.2.0 and 71b7a7d

Thanks for your time