Unify implicitNotFound and regular string interpolation

[scabug]

Having all these annotations running around with interpolated-strings-which-aren't does not feel good. @implicitNotFound should be "reimagined" in some form which is consistent with string interpolation. In fact one could take the opportunity to generalize it properly so that creating better error messages based on interpolating annotation arguments and elements of the enclosing scope could be used by anyone who cared to.

Because right now it's just a little bundle of maintenance (see "object ImplicitNotFoundMsg" in implicits.)

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-7411?orig=1
Reporter: @paulp

[som-snytt]

tpolecat would care to craft a better message:

I have a nice setup but FQNs fq with it `Operation doobie.labs.qb.hidden.StateMachine.Having isn't permitted here. Allowed: doobie.labs.qb.hidden.StateMachine.Join with doobie.labs.qb.hidden.StateMachine.Where with doobie.labs.qb.hidden.StateMachine.Select`