fix(lib/epoch): use correctly very first slot number

[EclesioMeloJunior]

Describe the bug

• Currently, the VerificationManager.VerifyBlock method changes the epoch state if the header passed as argument is 1
• It does not make sense for the verification to change the epoch state
• Makes more sense to set the first slot at finalization as said here fix(lib/babe): fix setting first slot of network, fix loading BABE epoch params #1640

[ramiroJCB]

Hello @EclesioMeloJunior I wanted to pickup this ticket, But I saw this PR and I wanted to asked you if that pr solve this current issue ?

[EclesioMeloJunior]

hey @ramiroJCB yes, this issue is being addressed by PR #3841, another related task that can be addressed on top of that PR is the issue #3866, it is a simple issue that can be tackled by you!