search: aggregator merges file match results in report

Created by: keegancsmith

This is a refactoring that moves the merge logic from the invidual functions to the new report function. Additionally we implement true merge logic, rather than assumptions based on if we have a symbol vs filematch result.

There is one potential downside. We now allocate an intermediate "[]SearchResultResolver" slice. In practice I believe this won't be that big of an issue since the size of the interface "SearchResultResolver" is tiny compared to the size of a "FileMatchResolver".