Move Binary Incompatible instances and syntax into main traits for 2.0

[LukaJCB]

This involves moving the *InstancesBinCompatN into *Instances and moving *SyntaBinCompat into their respective type classes. :)

[kailuowang]

@LukaJCB I propose we remove the "help wanted" since this one is on hold, i.e. not ready? Just want to make life easier for people looking for Cats issues to contribute to.

[kailuowang]

hmm, these changes (removing a method from an existing trait or removing the trait all together) may be binary breaking.