Afform - SearchKit support for calculated fields

[colemanw]

Overview

Adds support for calculated fields as afform search filters. E.g. an aggregated field like SUM: Contribution Total Amount can now be dragged into the search form from the afform palette.

See https://lab.civicrm.org/dev/core/-/issues/2361

[civibot]

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[eileenmcnaughton]

This DID allow me to expose a having filter so I guess it does what was intended. I hit a couple of other things but I don't think they are regressive so I will clarify & log furher issues