refactor(language-service): Create ng.CompletionEntry to replace ts.CompletionEntry (#33379)

It is messy to keep casting `CompletionEntry.kind` from
`ng.CompletionKind` to `ts.ScriptElementKind`.

Instead, create a new type `ng.CompletionEntry` that is exactly the same
as `ts.CompletionEntry`, but with the `kind` type overridden to
`ng.CompletionKind`.

This way, we only have to cast it once, and can do so in a safe manner.

PR Close #33379

packages/language-service/src/language_service.ts

@@ -70,7 +70,8 @@ class LanguageServiceImpl implements LanguageService {
       isGlobalCompletion: false,
       isMemberCompletion: false,
       isNewIdentifierLocation: false,
-      entries: results,
+      // Cast CompletionEntry.kind from ng.CompletionKind to ts.ScriptElementKind
+      entries: results as unknown as ts.CompletionEntry[],
     };
   }