Context accessor method

[oskin1]

Helper method allowing to access dependencies in context in slightly more convenient way when there are multiple of them:

import tofu.syntax.context._
def foo[F[_]: Monad: Foo.Has: Bar.Has]: F[X] =
  (hasContext[F, Foo], hasContext[F, Bar]).mapN((f, b) => ???)

vs

def foo[F[_]: Monad: Foo.Has: Bar.Has]: F[X] =
  (Foo.access, Bar.access).mapN((f, b) => ???)