* introduce feedbacks hit tracking for testcases
* make Testcase::hit_feedbacks into Cow<&str> instead of String
rename get_hit_feedbacks to append_hit_feedbacks
update documentation
* simplify ConstFeedback
* rename Feedback::last_result to prev_result
* impl TODO prev_result for NewHashFeedback, ListFeedback, TransferredFeedback, NautilusFeedback
* rename prev_result to last_result
* add docs
* introduce Objectives hit tracking
* update docs
* update Cargo.toml docs
* update docs
* track Feedbacks & Objectives hit in Fuzzer::add_input
* fmt
* clippy
* fix type error in OomFeedback::last_result
* impl last_result for AsanErrorsFeedback
* add track_hit_feedbacks as a feature to libafl_libfuzzer_runtime
* fix clippy
* change return type of Feedback::last_result to a Result
* remove expect in NewHashFeedback::is_interesting
* move Error::premature_last_result to libafl from libafl_bolts
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