Don't use packageManager field

[nlordell]

This PR removes the use of the pacakgeManager field for a couple of reasons:

• corepack stuff is experimental (source)
• It only supports exact versions - so updating our package manager locally can lead to

Instead, I changed to use the engines field that will produce warnings on incompatible versions.

I also removed the safe-contracts exception by solving the lints. It also means we have an ultra-consistent Safe contracts version that we use across all our modules (which has some nice benefits).