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