Unstaking didn't actually work because it was using `transferFrom()` on the
`StakeVault` with the `from` address being the vault itself.
This would result in an approval error because the vault isn't creating
any approvals to spend its own funds.
The solution is to use `transfer` instead and ensuring the return value
is checked.
This commit migrates the repo to our foundry template, which ensures we
have consistent tooling across smart contract repositories that are
maintained by Vac.
This removes all hardhat related files and workflows and replaces them
with more perfomant foundry workflows.
It also sets up tests, CI and linting.
Ricardo Guilherme Schmidt
r4bbit