Most of @itwin/core-react was already replaced by iTwinUI. We should deprecate the remaining components and APIs from this package in preparation of package removal. In case the API is still needed and there's no available replacement - move it to @itwin/components-react.
### Tasks
- [x] Deprecate `Popup` in favor of `iTwinUI` `Popover`
- [x] Move remaining components to other packages
Describe the Solution you'd like
Most of
@itwin/core-reactwas already replaced byiTwinUI. We should deprecate the remaining components and APIs from this package in preparation of package removal. In case the API is still needed and there's no available replacement - move it to@itwin/components-react.