Obtain Components using the fastest method

There are several variations of the GetComponent() method, and they each have a different performance cost, so it becomes prudent to call the fastest possible version of this method. The three overloads available are GetComponent(string), GetComponent<T>(), and GetComponent(typeof(T)). It turns out that the fastest version depends on which version of Unity we are running since several optimizations have been made to these methods through the years; however, in all later versions of Unity 5 and the initial release of Unity 2017, it is best to use the GetComponent<T>() variant.

Let's prove this with some simple testing:

int numTests = 1000000;
TestComponent test;
using (new CustomTimer("GetComponent(string)", numTests)) {
  for (var i = 0; i < numTests; ++i) {
    test = (TestComponent)GetComponent("TestComponent...