The previous version of this query inadvertently excluded constants
which weren't classes or modules. This version includes them, by
introducing a laxer version of `resolveScopeExpr` that doesn't require
the result to be a `TResolved`.
By convention, instance variables are considered to be "defined" in the
`#initialize` method of their containing class. If an instance variable
is written to in `#initialize` and then read elsewhere in the program,
we will point from the read to the write. If it is not written to in
`#initialize` then we won't provide any jump-to-definition information
for it.
