Give EventLogging total control of whether to include itself on mobile

EventLogging has been running without problems for some time
It should be given full control of itself in MobileFrontend
This removes $wgMFLogEvents from MobileFrontend

Bug: 50145

Change-Id: I2f49ad6b8eadb166728d82fabf06613fd75553e9
Merge "Give EventLogging total control of whether to include itself on mobile"