Use EditInPlace control for Identity Server picker to improve a11y

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Extracted from #29272 to reduce changeset size.

As before this uses an EditInPlace control to show an error state with a proper error message.

Before	After

Checklist

• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• I have licensed the changes to Element by completing the Contributor License Agreement (CLA)

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Browser support for this is now okay https://developer.mozilla.org/en-US/docs/Web/CSS/:not#browser_compatibility.

I caused a bug here, and it was borderline unreadable before, having a list of selectors like this makes this a bit easier to parse.

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Approval via https://matrix.to/#/!oqOIeEMggmJDUIJWHb:matrix.org/$hTFQixgjvvtbvENHE9Z7oP31lGJKc80D-l6S9om8FUQ?via=element.io&via=matrix.org&via=half-shot.uk

However we should rethink the phone and email fields above this input, as it's quite jarring for them to pop-in. #29330