sophia: more precise split operation.

do not account meta data size in split operation.
sophia: proper in-memory index version update.

Handle a possible situation when in-memory key version
might have LSN lower or bigger than update key.

lower:  default sequential work case;
bigger: merger key redistribution;
(iterator stream starts insert versions with bigger LSN)
sophia: do svv gc in merge key redistribution
Merge branch 'dev' into ctl-refactoring
sophia: use global LSN instead of LSVN in single-stmt transaction