Make RandomE support IReadOnlyList<T>

[bluexo]

This PR make RandomE support IReadOnlyList

GetReadOnlyRandom(this IReadOnlyList list);
GetReadOnlyRandom(this IReadOnlyList list, IReadOnlyList weights);

[BasmanovDaniil]

Hello! Thanks for the contribution, good idea. A few years back I didn't want to reference LINQ library, to minimize dependencies and memory footprint. I think I might have used it in one of the examples anyway, I will need to investigate it a bit. The situation with Unity is completely different now, maybe I will just go with it. I will try to take a look at it this weekend, but might have to postpone it to after new year celebrations.

[BasmanovDaniil]

Hey @bluexo! Finally was able to take a look at this idea.
Seems like it is a fairly common and complex issue: dotnet/runtime#31001
The simplest solution I see is to just replace IList with IReadOnlyList in the relevant methods, it shouldn't break much.
But I have some other ideas that might be just as valid, can you provide an example of your use case?

[bluexo]

Hey @BasmanovDaniil! Thanks for your reply, I often use the List like this:

  public SomeClass : MonoBehaviour
  {
          public IReadonlyList<int> ListProperty => listField;
          [SerializeField]
          private List<int> listField;
  }

So , I don't want someone modify the private field.