fix(tabs): hidden tabs don't render expansion panels correctly

[tiaguinho]

Fix issue #5269

[josephperrott]

Can you provide a test to verify this is fixing the issue as described?

I don't believe this will fix the issue as expected as immediate attachment of the tabs content does not cause the animations to run as expected so the expansion panels will still look incorrect.

[tiaguinho]

@josephperrott I just add the test to demo app.

[josephperrott]

In looking closer at this change, we actually can't do this change as it is a major change to the workings of material tabs. This change immediately attaches all of the tab bodies to the DOM, which places more items in the DOM that are needed.

[tiaguinho]

When I made the change, I see this problem too. This probably will reduce tabs performance because all the bodies are attached to the DOM.
But fixing the bug isn't better than have performance with a bug?
This can't be a workaround until we find a better solution?

[josephperrott]

We determined that it is more valuable to not change the functionality back and forth between the two concepts. Also in the near future we should be able to land #6832 which also could be used as a workaround.

[tiaguinho]

Ok.
Thank you.

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