Implement an LSP Server for FTL

[worstell]

• Create lsp server in code to process schema.Errors and publish to lsp client (feat: Add LSP for FTL #1150)
• Parse out error location in file to only highlight the word reported by FTL #1158
• Implement a Listener interface that allows listening to buildengine events (feat: Add LSP for FTL #1150 )
• Ability to handle errors from any language runtime #1159
• Add mechanism to track and clear diagnostics #1160

Ideas: Listener interface

type Listener interface {
  BuildComplete(errors []schema.Error)
}

//perhaps with convenience helpers to make it easier to use?
type BuildCompleteListenerFunc func(errors []schema.Error)

func (b BuildCompleteListenerFunc) BuildComplete(errors []schema.Error) { b(errors) }

With that cmd_dev could just listen for events and sent to the LSP rather than injecting the LSP into buildengine. This should help reduce coupling.

Ideas: For handling errors from all language runtimes

1. Create GRPC server and runtimes push errors back as they build
2. Come up with some protocol that we can use to talk with builds over stderr
   • output json and that json has the structured errors in them
   • probably the easiest approach