MINOR: stream: Save the last filter evaluated interrupting the processing

MINOR: stream: Save the last filter evaluated interrupting the processing

It is very similar to the last evaluated rule. When a filter returns an
error that interrupts the processing, it is saved in the stream, in the
last_entity field, with the type 2. The pointer on filter config is
saved. This pointer never changes during runtime and is part of the proxy's
structure. It is an element of the filter_configs list in the proxy
structure.

"last_entity" sample fetch was update accordingly. The filter identifier is
returned, if defined. Otherwise the save pointer.