This was a bandaid solution to easily allow for upgrade scripts.
We've changed those now to expect environment variables instead.
This allows us to change the dependencies without committing them to
version control.
This renames `RewardsStreamerMP` to `StakeManager`. The original name
only exists because the project has started with different versions of
the contract. Since the contract is no longer just dealing with MPs but
actually distributes rewards, it makes sense to make this the official
stake manager of the protocol.
**BREAKING CHANGE:**
- `RewardsStreamerMP` is now `StakeManager`
- `StakingManager__*` error selectors are now `StakeManager__*`
selectors
