Improve performance using reference, not cloning

[mathbalduino]

The performance (may be) improved if the logger holds a reference to it's parent, instead of cloning the entire base fields, preHooks, postHooks and outputs slices/maps.

At the useReference branch, there's some suggestion:

type hooksChain struct {
	parent *hooksChain
	hooks  Hooks
}

If this struct is used inside the logger struct, replacing the old baseFields, preHooks/postHooks and outputs field types, they will continue to have the same behavior.

[mathbalduino]

This will only help async loggers, since the work still needs to be done. It may be even worse, because we'll need to use no-tail recursion.

We're basically just moving the overhead from the log cloning to the post-hooks phase, that may be executed asynchronously...

[mathbalduino]

useReference branch was deleted, because it was too old. Do it from scratch, if it is really needed