Add refactoring action to convert stored to computed properties

[ahoppen]

This is the first syntactic refactoring action that needs to perform a cursor info request on codeAction/resolve, so the majority of this PR is to add infrastructure for that.

Based on #2496.

[ahoppen]

@Padmashree06: It looks like the refactoring action in swift-syntax doesn’t produce correct whitespaces here (it should be x: Int, not x :Int). Would you be able to work on a fix for that in swift-syntax?

[Padmashree06]

Yes sure! I will fix it!

[Padmashree06]

@ahoppen I have fixed the whitespace error in swift-syntax.

[ahoppen]

@swift-ci Please test

[rintaro]

As I mentioned in #2588 (comment), I don't think we should allow arbitrary cursorInfo in textDocument/codeAction request.
If the client don't support codeAction/resolve for .edit, imo we should drop this action.

[rintaro]

IMO the whole mechanism should be something as simple as:

protocol SyntaxCodeActionProvider: SendableMetatype {
  // Provider name. default impl: { String(describing: Self.self) }
  static var name: String

  static func codeActions(in scope: SyntaxCodeActionScope) -> [CodeAction]
  static func resolve(_ codeAction: CodeAction, in snapshot: DocumentSnapshot) -> CodeAction
}

struct UnresolvedCodeActionData: LSPAnyCodable {
  // Provider name generated the code action.
  var provider: String

  /// The document on which the code action should be applied.
  var document: VersionedTextDocumentIdentifier

  // Original `CodeAction.data` attached.
  var orignalData: LSPAny?
}

func codeAction(_ req: CodeActionRequest) -> CodeActionRequestResponse {
  let actions = [(provider: SyntaxCodeActionProvider.Type, action: CodeAction)] = ...

  return .codeActions(
    actions.map { item
      if shouldResolve(item.action) {
        var action = item.action
        action = UnresolvedCodeActionData(provider: provider.name, codeAction: action.data)
        return action
      } else {
        return item.action
      }
    }
  )
}

func codeActionResolve(_ req: CodeActionResolveRequest) -> CodeAction {
  var codeAction = req.codeAction 
  let data = UnresolvedCodeActionData(fromLSPAny: codeAction.data) else {
    return codeAction
  }
  let provider = getCodeActionProvider(name: data.provider)
  codeAction.data = data.originalData
  return provider.resolve(
    codeAction, in: getSnapshot(data.document) // Probably with some more context to request `cursorInfo`.
  ) 
}

Each SyntaxCodeActionProvider should be able to store abitrary LSPAny information necessary for resolving the action, as the CodeAction.data.