Modify check for no guardians & add tests

[JohnGuilding]

Builds upon changes slightly from ca7d21c and adds tests

1. Only calls setupGuardians if guardians.length, weights.length, and threshold are all 0. It felt appropriate that no guardian weights should be passed in if the guardians themselves are not known. And passing the threshold also felt like it could be redundant without knowledge of guardian count and weights. The logic added in commit ca7d21c failed when running a test with no guardians passed in because of conflicting checks in setupGuardians. Permitting weight and threshold also be zero and adding the check in configureRecovery keeps the setupGuardian function simple.

2. Adds guardianConfig.initialized checks in existing tests

3. Adds tests for new logic in configureRecovery.t.sol

[SoraSuegami]

You removed && guardianCount > 0 because setupGuardians will be never called in configureRecovery when no guardian is set, right?

[JohnGuilding]

Yes exactly