Arguments only used in `update` hook are not tracked

[Francesco Novy]

It took me some time to figure it out, but it seems that arguments only used in the update hook (no matter if named or positional) are not properly tracked.

I made a failing test case here:

mydea@4b051ca

E.g.:

 class extends Resource {
        @tracked value;

        setup() {
          this.value = this.args.positional[0];
        }

        update() {
          if (this.args.named.shouldReload) {
            this.value = `${this.args.positional[0]} RELOADED`;
          }
        }
      }

Changing shouldReload will not trigger the update.