`extract` with `EXTR_SKIP` should not override existing types

Bug report

when EXTR_SKIP is passed to extract we should not change types for variables we know exist

inspired by vimeo/psalm#7361

Code snippet that reproduces the problem

https://phpstan.org/r/03a0f64a-8ac5-446e-b502-a899219e5691

Expected output

2x same type dumped

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