Drop support for history file version 1.
ParseExecutionContext no longer contains an OperationContext because in my
first implementation, ParseExecutionContext didn't have interior mutability.
We should probably try to add it back.
Add a few to-do style comments. Search for "todo!" and "PORTING".
Co-authored-by: Xiretza <xiretza@xiretza.xyz>
(complete, wildcard, expand, history, history/file)
Co-authored-by: Henrik Hørlück Berg <36937807+henrikhorluck@users.noreply.github.com>
(builtins/set)
