swift234

Rearrange how CalleeCandidateInfo processes candidates in its list, to
make sure that properties and subscripts have a self type in their tracked
type.  This makes SubscriptExpr processing more logical (given that it applies
both self and an index list), by putting hacks in more principled places.

It would be great to someday eliminate SubscriptExpr entirely, but this isn't
going to happen in the short term.  NFC.