Allow soldeer commands to run outside of the project root

[beeb]

Currently, soldeer assumes that the dependencies dir, the lock file, the foundry config file, the soldeer config file and the remappings file are localed in the current working directory. We could allow for more flexibility (running soldeer commands from a sub-directory) by traversing the file tree upwards until we find a foundry project root (a folder that contains a foundry.toml or soldeer.toml file), instead of using env::current_dir().

[mario-eth]

maybe a better idea is to have an arg? I'm not sure if traversing upwards is the right approach.

[beeb]

It's not a great UX if a user has to pass an additional arg if they want to run soldeer install package~version from the src or test directory (that's an example).

Besides, this is how foundry does it

[mario-eth]

Hmm, ok, then we should do it this way then.