Remove Wildcard from Expr

[findepi]

Wildcard is not an expression. It should not be part of Expr enum

it doesn't even have a type

datafusion/datafusion/expr/src/expr_schema.rs

Lines 214 to 218 in 68e372f

	Expr::Wildcard { .. } => Ok(DataType::Null),
	Expr::GroupingSet(_) => {
	// Grouping sets do not really have a type and do not appear in projections
	Ok(DataType::Null)
	}

I also think it's necessary to move the ExpandWildcardRule to the builder.

That would be great!

That could potentially unlock removing Expr::Wildcard. It's not really an expression (just like Expr::Alias isn't #1468 and Sort weren't #12193)

Originally posted by @findepi in #14380

[findepi]

i changed the title of #7765 to better reflect it already covers removal, not only deprecation