Allow an infer type node to resolve its own name

[weswigham]

infer X normally makes X available in an adjacent scope - namely the containing conditional's true branch. However, typically, a declaration should be capable of resolving to its own name. With this change, resolving X within the context of infer X, will actually result in X's symbol, rather than an undefined (or, more confusingly, an outer scope) result.

Fixes #40362