`approx_distinct` should be leveraging dictionary encoding to support faster counting for these types

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

A challenge to improve `approx_distinct`, which should be leveraging dictionary encoding to support faster counting for these types.

**Describe the solution you'd like**

Making sure we can use the cardinality of the dictionary to speed up.

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
Add any other context or screenshots about the feature request here.

Start by locating the Rust implementation of `approx_distinct` and the dictionary-encoding code paths in DataFusion. Determine which supported types expose dictionary cardinality and define completion as using that cardinality to make counting faster, with coverage for the affected types.

Written by the indexing model from the issue text.