Provide ability to score based on date relativity instead of recency only [#3523237]

Problem/Motivation

Sometimes it is desirable to sort a view based on the difference between the value in a row's datetime field rather than just simply the recency of the value.

Proposed resolution

Provide a configuration option for datetime fields to choose between recency and relativity, and update the service to process the information

Issue fork views_scored_sort-3523237

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datetime-relativity changes, plain diff MR !4
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