Filtering types at call edges to handle tuples better.

[victornicolet]

This adds a filter check at the level of outgoing edges from a call node, where the tuple index information is present. This allows for more precise filtering. For example, if you specified that a function source(...) (Value, error) is a source but also specified that error values are filtered out of the dataflow tracking, this will now filter out using the second part of the output tuple of the calls to source.