support import $exec in Ammonite scripts

[chessman]

Describe the bug

https://ammonite.io/#import$exec

This is similar to import $file, except that it dumps the definitions and imports from the script into your REPL session. This is useful if you are using a script to hold a set of common imports: using import $file to import a script doesn't propagate imports from that script into your REPL.

To Reproduce

Steps to reproduce the behavior:

imports.sc

object Imports {
  def hello() = println("hello, world!")
}
import Imports._

script.sc

import $exec.imports
hello()

Metals shows an error: "not found: value hello".

Expected behavior

Metals shows no errors.

Installation:

• Operating system: Linux
• Editor: Emacs
• Metals version: v0.10.8

[tgodzik]

Thanks for reporting! Normally ammonite generates special files that we can use to make it all work with the $file imports. This doesn't seem to happen with $exec, not sure where it can be handled. @alexarchambault any pointer where we should look?