Function singnatures, cleanup of benchmarks, renaming of clashing test names, test patterns, more complete DB

[msooseth]

This fixes/adds:

• Function signatures are now passed to the solvers. This was missing and is required for HEVM to only explore the specific functions for non-dstest contracts
• Benchmarks had unused code (e.g. "test..." where we had a "prove..."), and some had commented-out code. Fixed.
• Benchmarks sometimes clashed on contract names. This has been fixed
• Case printing is a lot cleaner now
• Graphs subdirectory is now ignored in .gitignore
• Tests can be selectively run using --tests REGEX
• HEVM shell scripts marks test as UNKNOWN when we can only partially execute it due to e.g. call to symbolic code
• A test for the keccak length issue has been added.
• BadVault test by @karmacoma-eth

Warning: this is a breaking change, the database now contains the function name and the signature as well. This is hopefully the last breaking change.