When the `ts.Project` creates the language service plugin (in this case,
the Angular Language Service), it sets the project's language service to
the new language service returned by the plugin create:
https://sourcegraph.com/github.com/microsoft/TypeScript@b12af0fa2bbd4b015e59adcfb49988cea7f919a1/-/blob/src/server/project.ts?L2035-2044

The project may be reloaded in response to various events, such as a
change to the tsconfig file, which then recreates the plugin. When this
happens, the language service that gets passed to the plugin `create`
function will not be the typescript language service, but rather the
previous instance of the new language service returned by the last call
to `create`.

This commit ensures that subsequent calls to `create` for the
`NgLanguageService` plugin for a project after the first call are able
to retrieve and hold on to the _TypeScript_ language service.

fixes https://github.com/angular/vscode-ng-language-service/issues/1923

PR Close #51912