add call sequence mutation that copies and repeats a call

[0xalpharush]

https://github.com/crytic/medusa/blob/master/fuzzing/fuzzer_worker_sequence_generator.go
https://github.com/crytic/echidna/blob/2c72579e72eb2818d63c60a11180e7359f9984e4/lib/Echidna/Mutator/Corpus.hs#L37
https://github.com/crytic/echidna/blob/2c72579e72eb2818d63c60a11180e7359f9984e4/lib/Echidna/Mutator/Array.hs#L43-L51

We may also want to do the same for solidity array (repeat element in a list)

[0xalpharush]

Add a new generator callSeqGenFuncDuplicateAtRandom which duplicates a call seq. elem at index N and inserts it at N+1. Will be helpful to reference existing implementation

medusa/fuzzing/fuzzer_worker_sequence_generator.go

Line 356 in 7b67ceb

func callSeqGenFuncCorpusTail(sequenceGenerator *CallSequenceGenerator, sequence calls.CallSequence) error {