Makes `["match", ["get", k], label, match, otherwise]` equivalent to `["case", ["==", ["get", k], label], match, otherwise]`. This changes the behavior of match expressions where the runtime type of the input does not match the type of the labels: previously such expressions produced a runtime type error and then fell back to the property default value; now they produce the fallback value from the match expression.

We can now take advantage of the relaxed typing for == and match, which allows full-fidelity conversion of categorical functions. Previously, we were relying on the default value being substituted at evaluation time if the input was not of the expected type. Now, case/match can handle that.