• Closes Don't export record constructor names #3328

This pr makes an important breaking change to the Juvix scoper. Previously, when defining a type, the constructors were put into the current scope. After this pr, they must be accessed through the type module that is generated.

E.g.

type Unit := unit;

-- BEFORE
fun : Unit := unit;

-- AFTER
fun : Unit := Unit.unit;
-- or
open Unit using {unit} public;
fun : Unit := unit;

Additionally, this pr adds the option --migration to the juvix format command. This option takes the identity of some migration we want to apply. For the purposes of migrating the existing codebase, I've added the export-constructors migration. When this option is given, the juvix formatter automatically adds an open statement after each type definition.
E.g. Run juvix format --migration export-constructors Example.juvix.

module Example;

type T := a | b;

Result:

module Example;

type T :=
  | a
  | b;

open T using {a; b} public;

Using this method to migrate is not guaranteed to succeed, and manual adjustments might need to be made.

1. Forward references to constructors need to be qualified. E.g.

syntax operator :: cons;  -- BEFORE
syntax operator List.:: cons;  -- AFTER

type List (A : Type) :=
  | nil
  | :: A (List A);

3. Another thing to consider is that the migration should not be run twice on the same file, because then there will be repeated redundant open statements:

open List using {nil; ::} public;

open List using {nil; ::} public;

I created a fish script for this:

#!/usr/bin/env fish

cd ./tests
for dir in (fd -a -t f "Package.juvix" | xargs -I{} dirname "{}")
    set witness "$dir/.migrated"
    if test -e $witness
        echo "Already processed: $dir"
    else
        echo "Processing $dir"
        if juvix format  $dir --migration export-constructors --in-place
            touch $witness
        end
    end
end