Activator performance improvement

Shouldn't close the previous PR early. Turns out I did not have to change much of my design.

Pinging previous trackers
@pranavkm
@halter73 
@rynowak
@ipjohnson
@yishaigalatzer 
I understand that. We should be using the registered ITypeActivator in ServiceProvider. Just use the TypeActivator type directly. No recursion. Way less complicated.