journal on-the-fly deserialization: support in journal

Knot.files

src/knot/Makefile.inc

src/knot/journal/chgset_ctx.c

src/knot/journal/chgset_ctx.h

src/knot/journal/journal.c

src/knot/journal/journal.h

src/knot/journal/serialization.c

src/knot/journal/serialization.h

src/knot/zone/zone.c

src/knot/zone/zone.h

tests/knot/test_journal.c