Port to Langium

[lars-reimann]

Is your feature request related to a problem? Please describe

Initially, Safe-DS was intended to be used from Eclipse, but we found the developer experience to be lacking. With the increasing popularity of LSP, we eventually removed Eclipse support and instead implemented an extension for VS Code. The LSP features of Xtext made this switch easy. But there are still several issues:

1. The server-side uses the JVM, the client-side uses web technologies.
   • More difficult for developers
   • Users of the extension need to install a JRE
2. Many LSP features are missing in Xtext
3. Hard to find documentation since we don't use the LSP directly but only interact with it via Xtext

Desired solution

Langium seems to solve all those issues. The short-term roadmap also is very promising. It would also ease the implementation of a graphical language.

Tasks

• Initialize component
• Port grammar
• Port formatter to Langium #513
• Port scoping to Langium #540
• Port type computer to Langium #541
• Port generator to Langium #542
• Port validation to Langium #543
• Port partial evaluator to Langium #603

Additional context

• Migration guide
• Discussion about uses of Xtext