Retrieving local rename ranges and the local rename refactoring both had
almost identical methods, except for the addition of retrieving the
outermost shadowed decl that was added a couple months back. Merge them.
Resolves rdar://106529370.
Update rename to pull the outermost-declaration so that references are correctly found.
Rather than keeping suppressed locations in the current parent, keep
them for the whole index. Local rename starts the lookup from the
innermost context it can, which could be a closure. In that case there
is no parent decl on the stack and thus no where to store the locations
to suppress. We could have a specific store for this case, but there
shouldn't be that many of these and they're relatively cheap to store
anyway.
Resolves rdar://104568539.
