Move EndpointEnablementProvider and EndpointEnablement

[philwebb]

I think EndpointEnablementProvider and EndpointEnablement are just used for conditions. We can probably move package and make them package private.

[wilkinsona]

As things stand EndpointEnablementProvider is used by EndpointProvider so the current usage isn't limited to conditions.

[snicoll]

If EndpointProvider moved in the same package as the condition that would be possible. If that's not too weird, I think it'd be better for those two classes to be private (I meant it that way originally).

[philwebb]

I missed EndpointProvider. I'll take another look.

[wilkinsona]

#10176 took care of this.