Move eth mapping creation to a background task

[elmattic]

Summary of changes

Changes introduced in this pull request:

• Add Ethereum mapping populate task in background
• Add status to /readyz endpoint
• Add new subcommand forest-cli healthcheck.

$ curl "http://127.0.0.1:2346/readyz?verbose"
[!] sync incomplete
[!] epoch outdated
[+] rpc server running
[!] no eth mapping

Reference issue to close (if applicable)

Closes

Other information and links

Change checklist

• [x] I have performed a self-review of my own code,
• [x] I have made corresponding changes to the documentation,
• [x] I have added tests that prove my fix is effective or that my feature works (if possible),
• [x] I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

[hanabi1224]

I believe Calibnet eth mapping check CI task needs to be re-enabled

[elmattic]

I believe Calibnet eth mapping check CI task needs to be re-enabled

Why do you think it should be re-enabled in this PR?

Let's re-enable it here, but we need to merge #4523 before.