feat(RewardsStreamerMP): make RewardsStreamerMP upgradeable

[0x-r4bbit]

This commit introduces upgradeability of the RewardsStreamerMP contract by leveraging the UUPS pattern.

This means, for deployment, we have to first deploy an instance of RewardsStreamerMP contract as a "template" logic contract and then create a ERC1967Proxy that points to it.

The proxy ensures the implementation address is stored in a deterministic storage slot.

This will later be leveraged by the StakeVault contract to implement the functionality to leave the system in case there was a malicious upgrade.

A lot of this is based on @3esmit work done in #73 with these changes:

• Since we need access to ERC1967Proxy 's implementation address, we need a custom contract that exposes the address (because we can't read storage slots from external contracts within EVM)
• Since we can't use plain ERC1967Proxy, we can't easily use Open Zeppelin's UnsafeUpgrades. Furthermore, since we've been using UnsafeUpgrades (not Upgrades) we're not getting any of the safety features anyways. Also I didn't manage to make SafeUpgrades work
• Because of that, we have to manually deploy the implementation contract and the StakeManagerProxy and initialize it properly (this is done here in the changes)

Closes #22

Checklist

Ensure you completed all of the steps below before submitting your pull request:

• Added natspec comments?
• Ran pnpm adorno?
• Ran pnpm verify?

[3esmit]

Please, avoid creating a new PR next time, as it makes the review process more complicated.