feat(relevant sort): Relevant sort widget

[VladislavFitz]

Summary

Implementation of widget toggling the relevancy strictness search parameter within a virtual index search.
InstantSearch Core inlcudes:

• RelevantSortInteractor - smart sort priority toggling logic
• RelevantSortController - controller presenting the smart sort priority applied to the search and a toggle control
• RelevantSortPresenter - presenter transforming the smart sort priority state to its representation for a controller
• RelevantSortConnector - high-level component automatically establishing the connections between smart sort components
• DefaultPresenter.RelevantSort.present – default textual presenter

And connections between them:

• RelevantSortInteractor.SingleIndexSearcherConnection
• RelevantSortInteractor.MultiIndexSearcherConnection
• RelevantSortInteractor.ControllerConnection

InstantSearch provides out-of-box ButtonRelevantSortController including a label presenting the smart sort state hint and state toggle button.

[aallam]

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