Automatic LF code formatter

[petervdonovan]

Tasks:

• Implement missing cases in visitor pattern
• Implement line wrapping (Billy, Peter) -- (edit: @petervdonovan is making another pass at this)
• Preserve comments - @petervdonovan
• Allow the user to disable formatting for specific sections of their code (see comments below) - @petervdonovan
• Add CI check that applies formatter to all *.lf files in the test directory and checks for equivalence (@lhstrh)
• Add methods for testing semantic equivalence of AST subtrees
• Rename org.lflang.lfc to org.lflang.cli - @billy-bao
• Create lff package and create lff application that applies formatter - @billy-bao
• Factor out WIP toward new FedGenerator (to be submitted in a separate PR)

[petervdonovan]

Can we try to merge this soon?

I promise that the change I just made was trivial and that this has mostly just been awaiting review for 23 days.

[lhstrh]

Sorry, this was not on my radar as my review wasn't requested. I'll have a look at this soon. I agree, we should get this merged...

[lhstrh]

This looks great and almost ready to merge! 🚀 🚀 🚀 I left a few comments. The formatting of the tests looks excellent to me, modulo a single bike shedding issue: semicolons. I believe it makes sense to enforce them in the LF code if the target requires them, and I recall @edwardalee expressing the same preference.