New UNIQUE_VALUES function for calculated column capabilities

The CalculatedFunction enum has a new value, UNIQUE_VALUES, which the schema describes as "Collect the unique values". It joins the existing MIN, MAX, SUM, MIN_MAX, NONE and COUNT_KEYS values, so a column's calculated capability can now be set to collect the unique values instead of only computing a minimum, maximum, sum or count.

CalculatedFunction is used in two places in the columns API. The function field of CalculatedCapability, returned in ColumnCapabilities.calculated, reports which function a column uses, and the function field of CalculatedCapabilityInput accepts it when you configure a column's calculated capability.

Because UNIQUE_VALUES can now appear in the function field of responses, clients that handle CalculatedFunction exhaustively, for example with a switch statement or a strict enum in generated types, should add a case for it. Otherwise a column that uses the new function can fail to parse or hit your default branch.