feat: Cache cargo-audit binary

[PythonGermany]

Only build the binary once and cache it to speed up subsequent workflow runs.

[marcoieni]

can you post some screenshots that show the performance improvement?

[PythonGermany]

With cache step but no prebuilt binary available:

With cache and prebuilt binary available

[PythonGermany]

There are other solutions I also tried out. Like using binstall, but I don't like the idea of introducing another 3rd party dependency if simple caching is also possible.

[PythonGermany]

One thing I am still not sure about if there could be any problems is if the newest version of cargo-audit changes

[marcoieni]

One thing I am still not sure about if there could be any problems is if the newest version of cargo-audit changes

oh you are right! Maybe using https://github.com/Swatinem/rust-cache would help here?
I.e. we cache rust artifacts instead of the binary.