Attachments/Blobs got deleted after compaction&re-sync

In CBSE-14861, Customer ran compaction and re-sync on CBLite device, caused attachments (blobs) to be deleted.

Customer observed this issue with CB lite core versions 2.8.4 and 3.1.1 when using Sync gateway version 2.8.4.

Also noted is an old, related, but unresolved bug, CBL-702.

Logs and database snapshots are attached in CBSE-14861

Two things we would like to add to CBL-4812: 

1. in CBL-4812, we tested by simulating the case with temporary tempering with ReplicatorLocalReplicator. We would like to add a test case.
2. In CBL-4812, there is a comment, "// This is not optimal. Consider to add a method to DBAccess, hasBlobReferences". Would like to have it in Beryllium.