Offer to download snapshots if Forest is run with an old or missing database

[lemmih]

Issue summary

Forest will not even attempt to sync to the FileCoin network if the database is too old or missing altogether. We only support network version >=16 and Forest knows attempts to sync from an earlier version will fail: https://github.com/ChainSafe/forest/blob/57599f7cf3051d92dec05107691b75afb5ccd944/forest/src/daemon.rs#L190-L208

To bypass this issue, users have to download a recent snapshot and use it to initialize the Forest database. To make Forest easier to use, it should ask the user for permission to automatically download and import a snapshot when necessary.

Task summary

• [ ] Use methods from #1846 to fetch the appropriate snapshots.
• [ ] Implement --assume-yes and --assume-no.

Acceptance Criteria

• [ ] When stdin is a tty and the database is not recent enough, ask to download the appropriate snapshot (either calibnet or mainnet).
• [ ] When stdin is not a tty, assume the user said no.
• [ ] When stdin is not a tty and --assume-yes is given, assume the user said yes.

Other information and links

Blocked by #1846