feat #4974 : venus : make snapshot optional

[LinZexiao]

Related Issues

#4974

Proposed Changes

check whether snapshot provide,and launch venus daemon correspondingly

Additional Info

Checklist

Before you mark the PR ready for review, please make sure that:

• All commits have a clear commit message.
• The PR title is in the form of of <PR type>: <#issue number> <area>: <change being made>
  • example: fix: #1234 mempool: Introduce a cache for valid signatures
  • PR type: fix, feat, INTERFACE BREAKING CHANGE, CONSENSUS BREAKING, build, chore, ci, docs, misc, perf, refactor, revert, style, test
  • area: venus, venus-messager, venus-miner, venus-gateway, venus-auth, venus-market, venus-sealer, venus-wallet, venus-cluster, api, chain, state, vm, data transfer, mempool, message, block production, multisig, networking, paychan, proving, sealing, wallet
• This PR has tests for new functionality or change in behaviour
• If new user-facing features are introduced, clear usage guidelines and / or documentation updates should be included in venus docs or Discussion Tutorials.
• CI is green