refactor(language-service): adds Symbol#typeArguments and does cleanup (#34571)

Adds a `typeArguments` method to the `Symbol` interface, cleaning up how
type parameters of a TypeScript type are currently found. This will be
necessary for providing completions for `$event` variables' properties
(#34570).

This commit also performs some fly-by cleanups seen while implementing
the `typeArguments` methods. There is more clean up to do in the
`typescript_symbols` file, but the scope of this commit didn't need to
get larger.

PR Close #34571

packages/language-service/src/global_symbols.ts

@@ -59,6 +59,7 @@ export const createGlobalSymbolTable: (query: ng.SymbolQuery) => ng.SymbolTable
             };
           },
           indexed: () => undefined,
+          typeArguments: () => undefined,
         },
       },
     ]);