[compiler] Always emit FuncDecl for outlined functions

Addresses follow up feedback from #30446. Since the outlined function is
guaranteed to have a module-scoped unique identifier name, we can
simplify the insertion logic for the outlined function to always emit a
function declaration rather than switch based on the original function
type. This is fine because the outlined function is synthetic anyway.

ghstack-source-id: 0a4d1f7b0a5a34f8ed68c463b1a153c51c3ea75e
Pull Request resolved: https://github.com/facebook/react/pull/30464