Change BlockIdentifier and BlockStatus types in the `starknet` pkg

[thiagodeev]

• make BlockStatus e an enum instead of string
• make blockIdentifier (in the PreConfirmed types) a uint64 (make sure in the sequencer code that it is really within the 64bit range)
• find other related improvements

[0xsamalt]

I would like to work on this issue and have made some progress for the same. I would appreciate if you can assign it to me.

[0xsamalt]

Hey @thiagodeev, quick update... opened two PRs against this issue: #3775 (BlockIdentifier to typed uint64) and #3779 (BlockStatus to typed enum). Both ready for review whenever you get a chance. Happy to make any changes needed!