Add accessibility to generate ctor intent

[dibarbet]

Support accessibility here - https://sourceroslyn.io/#Microsoft.CodeAnalysis.EditorFeatures/ExternalAccess/IntelliCode/Api/IIntentSourceProvider.cs,38

in the form of "Accessibility": "<one of these>"

[CyrusNajmabadi]

Closing out as speculative, and that we do not seem to be investing in intents anymore.