Add Lens' to the HasLog typeclass

[chshersh]

The HasLog typeclass has all functions required for implementing custom lens. Since lenses are reusable, because they are just type alias, I propose to add the following field to the HasLog typeclass with the default definition:

logActionL :: Lens' env (LogAction m msg)
logActionL = ...

So we need to introduce our own Lens' type alias (and reexport it) and add logActionL lens to the HasLog typeclass with the default definition (so people can implement their own definition if they want.

With this approach we won't depend on any *lens* package but still will provide lens-like interface using ideas from the following blog post:

• https://vrom911.github.io/blog/write-yourself-a-lens