Add 'InnerSpec.keys()' Method with Collection Parameter Support

[songkg7]

Summary

Supports collection type as a parameter to InnerSpec.keys(), and a few other method like this.

related: resolve #679

(Optional): Description

add method as follow:

public InnerSpec keys(Collection<?> keys) {
	keys.forEach(this::key())
	return this;
}

However, since the keys() method currently takes an Object as a parameter, I think we should approach method overloading very carefully.

How Has This Been Tested?

I written test code that takes a list as a parameter.

Is the Document updated?

No

[SooKim1110]

Thanks for your contribution!
If you don't mind, it would be great to have a similar method that accepts a collection as a parameter for values() and entries().