CDRIVER-2225: Execute BSON corpus Decimal128 parse error tests

Since d7406f5d, all parse error tests were
executing with bson_new_from_json(), which is only appropriate for type 0x00.

This commit also restructures the corpus test runner so that callbacks may be
provided for decode and parse error tests as they are for valid tests. This
change will make it easier to skip tests of any type, which will be necessary
for CDRIVER-2223.