feat!: bump `@openzeppelin/contracts` (4.9.2 ➡️ 5.0.0)

[guidanoli]

Necessary side effects:

• Bump solc to 0.8.20 (updated pragma)
• Adjust CartesiDApp and Authority, which inherit from Ownable (updated constructor)
• Adjust CartesiDApp which inherits from ReentrancyGuard (updated file path)
• Adjust tests to work with the new custom errors raised by OpenZeppelin contracts

Extra changes:

• Use the Address library in EtherPortal to send Ether to the DApp contract
• Remove the EtherTransferFailed custom error, and use OpenZeppelin's FailedInnerCall custom error instead
• Type dapp as address payable on IEtherPortal (function selector stays the same)
• Rename "owner" to "initial owner" in contracts that use Ownable
• Simplify portal unit tests (by mocking contracts)
• Remove ERC-721 receiver contract (not necessary for testing ERC-721 withdrawal vouchers)

Closes #161

[ZzzzHui]

With the upgrade of Ownable, we should also update comments here and here. Because now instead of 2, now there is only 1 OwnershipTransferred event emitted.

[ZzzzHui]

This branch needs a rebase

[guidanoli]

Rebased on top of main.