[Async] Load Player async asset type in LSP to accept async assets for validation

[sugarmanz]

Consume types done in player-ui/player#467 to power validation on Player content that contains an async asset:

{
  "id": "view",
  "type": "info",
  "title": {
    "id": "some-async-asset",
    "async": true
  }
}

Note that this is only targeting support for async assets. The base capability (AsyncNodePlugin) can support async nodes anywhere in the view AST, but the use cases have only been for asset-level async nodes. If use cases arise, we can look into fully featured validation support for any async node in the view AST.