Previously we always used content guarded by `$<LINK_ONLY:...>`
in `LINK_LIBRARIES`, even when evaluating for non-linking usage
requirements. Add a policy to honor `LINK_ONLY` in `LINK_LIBRARIES`
the same way we already do in `INTERFACE_LINK_LIBRARIES`.
Link line construction starts with `LINK_LIBRARIES` and appends
dependencies from the transitive closure of `INTERFACE_LINK_LIBRARIES`.
Only the entries of `LINK_LIBRARIES` are considered direct link
dependencies. In some advanced use cases, particularly involving static
libraries and static plugins, usage requirements need to update the list
of direct link dependencies. This may mean adding new items, removing
existing items, or both.
Add target properties to encode these usage requirements:
* INTERFACE_LINK_LIBRARIES_DIRECT
* INTERFACE_LINK_LIBRARIES_DIRECT_EXCLUDE
Fixes: #22496
Brad King