"Fixes a bug in partition_snapshot::merge_partition_versions(), which would not
attempt merging if the snapshot is attached to the latest version (in which
case _version is nullptr and _entry is != nullptr). This would cause
partition_version objects to accumulate if there was an older snapshot and it
went away before the latest snapshot. Versions will be removed when the whole
entry goes away (flush or eviction).
May cause performance problems.
Fixes #3402."
* 'tgrabiec/fix-merge_partition_versions' of github.com:tgrabiec/scylla:
mvcc: Test version merging when snapshots go away
anchorless_list: Make ranges conform to SinglePassRange
anchorless_list: Drop deprecated use of std::iterator
mvcc: Fix partition_snapshot::merge_partition_versions() to not leave latest versions unmerged
920131b2f7