feat: add support for empty list literals

[patientstreetlight]

The substrait proto definition provides a representation of empty list literals which is separate from the
representation of non-empty list literals:

message Literal {
  oneof literal_type {
    ...
    List list = 30;
    Type.List empty_list = 31;
    ...
  }
}

This change gives substrait-java a representation for empty list literals, along with conversions to/from
protobuf and to/from Calcite in Isthmus.

BREAKING CHANGE:

• ExpressionVisitor has a new method to visit Expression.EmptyListLiteral. Implementors which don’t extend AbstractExpressionVisitor will have to add their own implementation.
• Public class LiteralConstructorConverter now requires a TypeConverter to be passed to its constructor.
• ExpressionCopyOnWriteVisitor#visitLiteral() may now be called with Expression.EmptyListLiteral.

[CLAassistant]

All committers have signed the CLA.

[vbarua]

Overall this looks good. I do have some questions and suggestion in various places.

[vbarua]

Thanks for adding this in! Changes look good 🎉