Refactored libstagefright_frameDecoder_fuzzer

The following are updates to the fuzzer:
1. Systematized the order of API calls.
2. Added enums for relevant values.
3. Resolved fuzzer errors.
4. Added seed corpus for the fuzzer.
5. Coverage improved from 39.28% to 70.18%.

Test: ./libstagefright_frameDecoder_fuzzer
exec/s: 8
Bug: 331540179

Change-Id: I02342efd326828c97cccdb7d30762cc46182baa9