perf(injector): minor performance improvements

```
Before:
VM:
  DynamicInjectorBenchmark(RunTime): 414.8516905206389 us.
  StaticInjectorBenchmark(RunTime): 141.84397163120568 us.
dart2js:
  DynamicInjectorBenchmark(RunTime): 2765.193370165746 us.
  StaticInjectorBenchmark(RunTime): 1074.69102632993 us.

After:
VM:
  DynamicInjectorBenchmark(RunTime): 393.23633503735743 us.
  StaticInjectorBenchmark(RunTime): 114.91611123879568 us.
dart2js:
  DynamicInjectorBenchmark(RunTime): 2384.9821215733014 us.
  StaticInjectorBenchmark(RunTime): 884.5643520566122 us.
```
chore(DynamicInjector): removed reflactedType hack