Echidna 2.1.1

This is a release focused on fixes and minor features. User facing changes include:

• Optimized the memory usage during the fuzzing campaign.
• Added initial compatibility with invariant mode from Foundry.
• Added additional information on how Echidna spend time during startup.
• Fixed several small rare crashes.

This release also include a number of refactoring changes to make the code easier to improve in future.

Added

• Added missing space in ProcessorNotFound message (#977)
• Added measurement and log of external actions (#988)
• Avoid using cheat code address to form fuzzing call sequences (#993)
• Implemented invariant testing from foundry (#989)

Changed

• hevm upgraded to 0.50.4 (#986)
• Cleaned and improved codebase (#990, #994, #995, #997)
• Make frequently modified fields strict (#1000)
• Force corpus evaluation (#1002)
• Improved text/headless UI (#991, #1006, #1007, #1009)