Add supports for using Source Generator using Directives

[Perklone]

Address #610. Will be a Draft PR until we can get a conclusion regarding the design of how we want to approach having the source generator

This is a concept PR that I had in mind, also discussed with @bishabosha and @kannupriyakalra aswell.

The idea is that use the source generator via directives that would look something like this:

project.scala:
//> using sourceGenerator.scripts ${.}/generator/generator.scala <- This one for specifying the path of the generator
//> using sourceGenerator.excludeScripts true <- to make sure that the generator file is not run from the original scala-cli runner

in your generator file:

generator.scala:
//> using sourceGenerator.inputDirectory "${.}/../source-generator-input" <- Directory where the data file is located
//> using sourceGenerator.glob "glob:test.in" <- Type of files that will be taken to the Bloop Server

[Gedochao]

#3035
in case there's anything we can reuse, kudos to @MaciejG604

[Gedochao]

@Perklone @bishabosha
Hey, what's the status on this?
As far as I know, this should be unblocked on Bloop's side (cc @tgodzik).
Let me know if you need help.

[Perklone]

Hello, currently there are no update with this atm since I haven't found much time recently, hoping that I can continue sometime soon though.

[bishabosha]

no updates from me either

[bishabosha]

Hey @Perklone how is it going, would you consider picking this up again?

[Perklone]

I wanted to, but unfortunately still haven't got the time, if someone wanted to pick this up, i'll be okay with it. But if not, I'll try to work on it on weekends