This commit introduces a first version of a `VaultFactory` that later
will be extended to be capable of instantiating reward vaults and
possible keep track of vault instances per owner.
As a first step, this implementation comes with a `createVault()`
function which takes care of creating vaults.
Because `VaultFactory` also knows about `StakeManager` it can derive the
manager's address and stake token from it when creating vaults, allowing
the API to be without arguments.
Partially addresses #37
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.
