Add a way to access logical String ScalarValues as &str

[alamb]

Is your feature request related to a problem or challenge?

We hit a bug upstream in InfluxDB in pruning where we didn't match a certain kind of string ScalarValue

In this case , we want to access the underlying strvalue of a ScalarValue that holds a logical string (ScalarValue::Ut8 and ScalarValue::LargeUtf8 for example)

There are several types I know of (Utf8, LargeUtf8, Utf8View, and Dictionary(.., <...>)

Today we need to remember to check for all the relent types

Describe the solution you'd like

I would like a function on ScalarValue that does this -- so we don't have bugs when we forget to check for a type.

Describe alternatives you've considered

No response

Additional context

No response