This is a refactor of the below refactor.

Parts of this have now been merged as part of other PR. So in effect, this PR only makes one major change:

• in concrete grid search classes, overrides the "requires-fh-in-fit" tag in the constructor of the grid search algorithms with the value of the single component (the tuned estimator), using clone_tags.

A minor change is docstring linting in _tune.

This is a follow-on from #1088 attempting to address the incompatibility of the grid search refactor due to its "dynamic tag like" behaviour pre-refactor.

Apologies from working with the tags here, but this naturally emerged in trying to address issues and finish the forecaster refactor.

The solution I've adopted makes the following changes to the grid search algorithms:

• in concrete grid search classes, overrides the "requires-fh-in-fit" tag in the constructor of the grid search algorithms with the value of the single component (the tuned estimator)
• in BaseGridSearch, completes the refactor by moving all algorithmic logic to the _fit, _predict etc interface. This includes removing the override to the cutoff getter.

The first change, the override, is achived by new dynamic tag handling (object, not class) methods in the BaseEstimator class: getters get_tags, get_tag and setters set_tags and mirror_tags. These make use of dynamic tags that can be set in construction and override class tags and their inheritance.

The one other change is replacing the tag access in _set_fh by get_tag so it can see the dynamic tag override.