Besides the NodeTree case (which remains unchanged), the localize code
is only used in one place (to generate previews of shading data-blocks).
This commit introduces a new `LIB_ID_CREATE_LOCAL` option for ID
creation/copying, which essentially implements the behavior of the
removed `BKE_XXX_localize()` functions into regular mainstream ID copy
code. When this option is set:
- new ID is tagged with `LIB_TAG_LOCALIZED`;
- Some ID copying callbacks have specific behaviors, mainly the root
nodetree of shading IDs gets duplicated with specialized
`ntreeLocalize()` function.
Note that I would not consider getting rid of `ntreeLocalize` for now,
this function is recursive, which should ideally never happen within ID
management copying code (this introduces all kind of complications).
No behavioral change expected from this commit.
Bastien Montagne
874cf52c10