Improve ergonomics of physical expr lit

[alamb]

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

For logical expressions, you can create them using syntax like lit("foo")

However for physical expressions, you need to use the much more verbose syntax of lit(ScalarValue::Utf8(Some("foo")))

It would be nice to implement the same thing for physical expressions

Describe the solution you'd like
allow lit("foo") and equivalent for physical expressions

Describe alternatives you've considered
N/A

Additional context
Inspired by this comment: #2819 (comment)