set fork detector checkpoints on bootstrapper applyBlock

[AdoAdoAdo]

Reasoning behind the pull request

• bootstrapping after shuffling to other shards with equivalent proofs does not always succeed

Proposed changes

• after applying the previously stored block, if this block has proofs, set the fork detector correspondingly.

Testing procedure

Pre-requisites

Based on the Contributing Guidelines the PR author and the reviewers must check the following requirements are met:

• was the PR targeted to the correct branch?
• if this is a larger feature that probably needs more than one PR, is there a feat branch created?
• if this is a feat branch merging, do all satellite projects have a proper tag inside go.mod?