Create o.a.s.sql.expressions.UnresolvedNamedLambdaVariable, convert it to o.s.sql.Column and wrap with R Column. Used by higher order functions.
unresolved_named_lambda_var(...)
character of length = 1
if length(...) > 1 then argument is interpreted as a nested
Column, for example unresolved_named_lambda_var("a", "b", "c")
yields unresolved a.b.c
Column object wrapping JVM UnresolvedNamedLambdaVariable