OwnableValidator with better API and without the linked list

[egillh210]

In this version I've added a updateConfig method that looks like this:

function updateConfig(uint256 newThreshold, address[] calldata ownersToAdd, address[] calldata ownersToRemove)

A UI that has a section to manage your signers is likely to have some component where users can do the following operations:

1. Add a new key
2. Remove an existing key
3. Change the threshold

It makes sense to just provide the UI dev with an API that can take all of these things in one go, and not have to worry about mid-batch reverts due to ordering of operations as you do with the batched transaction of the more primitive methods (addOwner, removeOwner, setThreshold). That said, this contract still has those methods too, if we ever want to use them.

** Technical stuff **

• This version uses the EnumerableSet4337 instead of SentinelList4337.
• The enumerable set is a better fit for what this contract needs which is just (unordered) insertions, deletions, and lookups.
• Deletions are more painful in the SentinelList compared to the set (having to pass a reference to prev to delete an entry)
• All the signing methods remain exactly the same as in the original
• Copied the tests from the OwnableValidator.t.sol files, and all tests are passing.

(also, I think this implementation has much better structure/readability than the original one)