[AUTOMATIONS-CONTRACT] Extended Vesting Scheduler Tests (no unsigned commits)

[kasparkallas]

Continuation of: #1994

[hellwolf]

I noticed some tests failing. I suspect some flaky fuzzing tests. I will look into it when I have time.

[0xPilou]

The stateful fuzz test seem to fail on some occassion.
Also, the stateful fuzz test does not cover claimable schedules.
Do you want me to add this ?

[github-actions]

XKCD Comic Relif

Link: https://xkcd.com/2002

[kasparkallas]

After this PR, this is the test coverage output of forge coverage:

| File                                                                                                  | % Lines           | % Statements       | % Branches        | % Funcs           |
|-------------------------------------------------------------------------------------------------------|-------------------|--------------------|-------------------|-------------------|
| packages/automation-contracts/scheduler/contracts/VestingSchedulerV2.sol                              | 98.16% (160/163)  | 98.81% (249/252)   | 85.00% (68/80)    | 100.00% (30/30)   |

The lack of complete 100% coverage can be explained by having guard clauses for readability and defensive programming that never actually get hit.