This PR mainlines the current state of new GPUI2-based UI from the
`gpui2-ui` branch.
Included in this is a performance improvement to make use of the
`TextLayoutCache` when calling `layout` for `Text` elements.
Release Notes:
- N/A
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Co-authored-by: Nate Butler <iamnbutler@gmail.com>
Co-authored-by: Antonio Scandurra <me@as-cii.com>
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