Support module imports in Juvix REPL

[paulcadman]

This PR adds support for importing modules from within a Juvix project in the Juvix REPL.

The imported module is checked (parsed, arity-checked, type-checked etc) as normal and added to the REPL session scope. Any errors during the checking phase is reported to the user.

Notes:

• You must load a file before using import. This is because the REPL needs to know which Juvix project is active.
• You may only import modules from within the same Juvix project.

Examples

After launching juvix repl:

open import

Stdlib.Prelude> open import Stdlib.Data.Int.Ord
Stdlib.Prelude> 1 == 1
true

import as

Stdlib.Prelude> import Stdlib.Data.Int.Ord as Int
Stdlib.Prelude> 1 Int.== 1
true

importthen open

Stdlib.Prelude> import Stdlib.Data.Int.Ord as Int
Stdlib.Prelude> open Int
Stdlib.Prelude> 1 == 1
true

Line-terminating semicolons are ignored:

Stdlib.Prelude> import Stdlib.Data.Int.Ord as Int;;;;;
Stdlib.Prelude> 1 Int.== 1
true

• Closes Support open/import statements in the repl #1951