core: rename temporary spaces to data-temporary

Everywhere where we refer to temporary spaces we now say data-temporary.
This is because temporary spaces were never truly temporary because
their definitions would still be persisted and replicated and they
couldn't be created on read-only replicas. In a following commit we will
introduce a new fully temporary type of spaces, which will be just
called 'temporary', so this commit signifies this terminology change.

NO_DOC=renaming
NO_CHANGELOG=renaming
NO_TEST=renaming