Add tool to modify fuzzer corpora

[tuturu-tech]

This PR adds the ability to modify an Echidna or Medusa corpus based on certain conditions, save a corpus into a corpus "history" file, and restore a previously saved corpus.

It includes the following changes:

• New CLI commands:
  • modify-corpus: Modifies an existing corpus based on the fuzzer configuration or data provided via flags. The available conditions are:
    • --fuzzer-config: Fetches the maximum time delay, maximum block delay, or blacklisted functions defined in the fuzzer configuration file. Calls or call sequences that use a larger time/block delay than defined, or use a blacklisted function, are discarded.
    • --modify-senders LIST: Takes in a list of the format 0xoldAddress=0xnewAddress,..., and replaces the caller for all calls that use the oldAddress with newAddress
    • --filter-functions: Removes calls or call sequences that call functions that no longer exist. Currently supports only one target contract.
    • --mode delete_sequence | delete_calls: Defines how filtering is done, delete_sequence deletes the entire call sequence file if any call within it is invalid per the included rules. delete_calls only deletes the invalid call.
  • snapshot: Saves the provided corpus directory into a history.json file so it can be easily retrieved. E.g., in case we want to rollback the changes we made to the corpus. Available flags: --corpus-dir, --fuzzer
  • restore: Restores a corpus from the history.json file, it will override the directory where it was previously saved. Available flags: --list-history (lists all saved corpora with their hashes), --hash STR (takes in a hash of the corpus we want to restore)
• New parsers and a new class CorpusModifier were added to support the above features.
• pyYAML was added as a dependancy so we can process echidna .yaml config files

Before merging this PR further work should be done to:

• Sanity check modification of Medusa corpora (only tested Echidna so far)
• Create unit tests for each of the features
  • Unit tests for call deletion
  • Unit tests for sequence deletion
• Resolve ignored mypy errors
• Add support for multiple contracts when using --filter-functions Note: This is non-trivial in the case where we have multiple target contracts that might have functions with the same name.
• Add error handling to file system manipulation
• Fix bug where corpus directories are not properly saved when using delete_sequences
• Modify Medusa sequence nonces when using delete_calls and modifying senders

[0xalpharush]

Can we add some docs in markdown files (in docs/)? Can be migrated to proper documentation site later