feat: Add current block starting point

[antiyro]

Add support to start a Checkpoint instance from current block.
Something like last in "start" config.json entry should do the job.

[eytanlvy]

can I take this one?

[antiyro]

Yes I'll assign it to you!

[Sekhmet]

@betacodd you might want to try starting from #227 as your base, as this PR will likely impact this issue.

[eytanlvy]

@betacodd you might want to try starting from #227 as your base, as this PR will likely impact this issue.

thank you, I'll wait for it to merge

[Sekhmet]

@betacodd the PR was merged.

[Sekhmet]

@antiyro what should happen if you restart the server? should it continue from where it stopped or start from "current" again? if the latter it means it should also drop all data it fetched on previous runs.