fix: read_span_flatbuffer was leaking an example per invocation

Parser logic needs to use VW::finish_example() rather than simple deletion to get rid of examples because the incoming example_factory may be grabbing examples from the example pool.

vowpalwabbit/fb_parser/src/parse_example_flatbuffer.cc

@@ -11,6 +11,7 @@
 #include "vw/core/error_constants.h"
 #include "vw/core/global_data.h"
 #include "vw/core/parser.h"
+#include "vw/core/vw.h"
 
 #include <cfloat>
 #include <fstream>
@@ -112,7 +113,7 @@ bool read_span_flatbuffer(
     }
   } while (has_more);
 
-  delete temp_ex[0];
+  VW::finish_example(*all, temp_ex);
   return true;
 }
 

vowpalwabbit/fb_parser/tests/read_span_tests.cc

@@ -87,6 +87,8 @@ void create_flatbuffer_span_and_validate(VW::workspace& w, const T& prototype)
   VW::parsers::flatbuffer::read_span_flatbuffer(&w, buffer, size, ex_fac, parsed_examples);
 
   verify_multi_ex(w, prototype, parsed_examples);
+
+  VW::finish_example(w, parsed_examples);
 }
 
 TEST(FlatbufferParser, ReadSpanFlatbuffer_SingleExample)