Increase unit test coverage

[minghinmatthewlam]

Context and scope
Currently the validator manager contracts haven't kept up as much for unit tests, need to look into test coverage report for forge coverage and get it up to expectations. With our repo structure of having the tests live next to the source code instead of a root tests folder, the forge command would need some tweaks to get accurate test coverage report for just source files.

Discussion and alternatives
Find a reproducible command or script that can test the unit test coverage of the validator manager contracts. Or ideally, different components in this repo like teleporter as well, but not a priority to include for teleporter right now.

Add basic unit tests to bring test coverage up.

Open questions
Example command forge coverage --no-match-coverage "(mocks|teleporter|utilities|governance)"

[michaelkaplan13]

Additional cases to cover (non-exhaustive):

• Adding a delegator when a validator is pending removal
• Trying to completeDelegatorRegistration when a validator is each pending removal and completed
• Trying to initializeEndDelegator when a validator is each pending removal and completed
• endDelegationCompletedValidator for delegations pending added, active, and pending removed.

[geoff-vball]

Mostly completed. ValidatorManager still needs more coverage.