Auto merge of #25410 - pshaughn:ceupgrade, r=jdm

Implement CustomElementRegistry.upgrade

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An additional small change will be needed if whatwg/html#5126 lands, which will pass an infinite recursion test this is currently failing in custom-elements/upgrading.html (right now the test is asking for behavior that isn't in the spec).
The remaining test in custom-elements/custom-element-registry/upgrade.html is because it needs shadow DOM.

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #24989

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- [X] There are tests for these changes

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