use bucket seqnos in storage snapshot after initial build completion

1. There is a setting for indexer ("indexer.use_bucket_seqnos") to be able to use bucket seqnos for session consistent scans. As the initial build works on collection level, the storage snapshot during/after initial build use collection seqnos. After stream merge, as the index snapshot continues to have collection seqnos(till there are more mutations), the session consistent scans cannot use bucket seqnos.

2. Once the storage snapshot has bucket seqnos, the assertion disabled as part of MB-41909 can be enabled again.