fix: SetConFieldType could create ill-typed programs

[brprice]

When running this action, we don't run a full typechecking pass (for efficiency). Prior to this commit we could create ill-typed programs, by not taking into account directionality, since arguments to constructors may only be checkable, but the action may wrap those terms in a hole without adding an annotation.

Note that this would have been fixed in a different way by #931.

[brprice]

We hadn't noticed this before because this action is rarely exercised. In particular, it is not part of the OpenAPI, and is never an "offered" action. Thus it does not participate in our property tests which check all offered actions are actually accepted (whilst that runs with smartholes, and this bug only happens because we don't do a smartholes pass, it still would have been caught since the test checks that the result is well-formed (with SH) and that that final TC pass did not change the program, in ensureSHNormal)

@georgefst I believe you were looking into exposing the typedef actions via the OpenAPI. Will that make them "offered" actions, and thus be part of the existing pbt? (If not, what's your plan / what is needed to get them tested in our existing test?)

[georgefst]

@georgefst I believe you were looking into exposing the typedef actions via the OpenAPI. Will that make them "offered" actions, and thus be part of the existing pbt?

Yes. That should mean that almost all of ProgAction will be covered. The exceptions being those actions which we expose via other APIs (i.e. those which aren't used via the "action panel" in our frontend), such as CreateDef and AddTypeDef.