Implements [Feature #19000] This commit adds copy with changes functionality for `Data` objects using a new method `Data#with`. Since Data objects are immutable, the only way to change them is by creating a copy. This PR adds a `with` method for `Data` class instances that optionally takes keyword arguments. If the `with` method is called with no arguments, the behaviour is the same as the `Kernel#dup` method, i.e. a new shallow copy is created with no field values changed. However, if keyword arguments are supplied to the `with` method, then the copy is created with the specified field values changed. For example: ```ruby Point = Data.define(:x, :y) point = Point.new(x: 1, y: 2) point.with(x: 3) # => #<data Point x: 3, y: 2> ``` Passing positional arguments to `with` or passing keyword arguments to it that do not correspond to any of the members of the Data class will raise an `ArgumentError`. Co-authored-by: Alan Wu <[email protected]>