Separating anchored position and Overlay class

[jonrohan]

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What are you trying to accomplish?

Dialog overlay wasn't scrolling the body and fixing the header/footer properly. When the revert is applied, it's reverting to display: block; instead of the display: flex that it needs to be. I originally tried to fix this by seeing if there was a better option for display: revert; but that leads to other problems with the overlay not disappearing.

@supports selector(:popover-open) {
  .Overlay[popover]:not(.\:popover-open) {
    display: revert;
  }
}

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List the issues that this change affects.

Closes https://github.com/github/primer/issues/2375

Risk Assessment

• Low risk the change is small, highly observable, and easily rolled back.
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• Fixes axe scan violation - This change fixes an existing axe scan violation.
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Merge checklist

• Added/updated tests
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• Tested in Chrome
• Tested in Firefox
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🦋 Changeset detected

Latest commit: f566a4f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/view-components	Minor

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[keithamus]

These will change as getAnchoredPosition falls back to other sides so we might want to thoroughly test this and make sure it isn't regressing.

[jonrohan]

I couldn't find these classes in PVC or dotcom codebases. Maybe they were leftover from another iteration? I can pull into a separate PR if we want to test this change more thoroughly

[keithamus]

Must be a holdover then. Go ahead and 🔥 🔥 🔥