Add CodeAction interface

[mjbvz]

Part of #33555

Problem
Code actions are currently just a list of Command. These commands provide have no information about what the code action actually does. We'd like to be able to do the following:

• Sort code actions so that fixes for errors show up first
• Group code actions by type / by the error they fix
• Provide a better UI for code actions that tells users which actions address which problems in the code

Proposal
Introduce a new CodeAction interface that defines additional information about a code action. To start, I propose we add two additional field to this interface: a type and a list of diagnostics:

enum class CodeActionType {
    // Standard type. Would be used for existing CodeActionProviders that return Commands
    Default = 0 ,

    // Fixes a diagnostic in the CodeActionContext
    QuickFix = 1,    

    // Perform a refactorng
    Refactoring  =2
}

interface CodeAction {
    // Command the performs the action
    command: Command

    type: CodeActionType

    // List of diagnostics this code action resolves
    diagnostics?: Diagnostic[]
}

// cc @jrieken

[jrieken]

CodeAction type yes, in that shape probably not. Folks also want a preview of the textual changes, so instead/in addition to a command we should support text edits or a workspace edit. This needs proper thinking. @mjbvz What are your scenarios?

[mjbvz]

@jrieken Kai and I talked about this today and I've put together a more complete proposal based on that discussion: #34664

That proposal also would not provide workspace/text edits in its current form, but has been designed so that they could be accommodated in the future

[jrieken]

ok, closing this as dupe of #34664