The HTTP Filter fuzz target (#9401, #9400), ingests an HttpFilter protobuf to fuzz. The mesasge contains an embedded google.protobuf.Any that encodes the appropriate filter configuration protobuf as a serialized byte string.

In order for the fuzz engine to locate interesting (i.e. valid) HttpFilter messages with valid filter configuration bytestrings, a dictionary should be created for each unit-tested HttpFilter containing bytestrings that are used in tests. This will help gain coverage over interesting edge and corner cases tested in filter unit tests.

I propose adding a simple utility function to each filter unit test (that can either be added manually, or added to a base unit filter gtest class, but that would require manual toil) that will create and populate a filter_name.dict file in each filter test directory. These will be linked in to the bazel target rule for filter_fuzz_test.