Align cast logic betwee variant_get and cast kernel for utf8 type

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**

This is part of #8982 which wants to support the type utf8

**Describe the solution you'd like**

Align the logic of cast from/to utf8 in parquet-variant with arrow-cast

**Describe alternatives you've considered**

**Additional context**